The question is "round" not turn, thus using the warcaster feat, yes you can as specific>general. A staff wielding sorcerer with polearm mastery and warcaster, can cast a 1 action spell as reaction(instead of an opportunity attack) to a target who/which enters his reach(which is his immideate hexes/squares, 5feet). Also, through the usage of metamagic(quicken spell) you can cast 1 leveled spell+ 1 cantrip in your own turn, and another leveled spell with the method written above, thus a total of 2 leveled spells plus a cantrip in 1 round. Unless i am wrong but this is how i interpreted RAW so far.
If you have haste, or action surge, this can be further increased(or the thief subclasses final feature which effectively allows you to play 2 turns thus 2 spells+ 2 cantrips + reaction spell due opportunity trigger of warcaster, a total of 5 spells in a round/first round of combat even without haste)
It grants additional action, explanation about spell casting clearly says you can not cast more than 1 spells in your turn idd, but explanations take into account the base action count of a character class non modified by spells or spell like features, thus spells and spell like features become the "specific" in that regard.
A caster with no haste cast on him, no 2 levels of fighter, clearly has only 1 action per turn, thus it is clearly unable to cast 2 action costing spells(same goes for metamagic feat) thus you are right only cantrips can be used(unless you are using a charged wand to cast spells, as multiple item interactions is possible with multiple action granting spells and abilities)... So a fighter/mage with 3 actions(haste action surge can cast 1 single action spell plus 2 action costing cantrip, plus 1 bonus action costing cantrip, plus 1 action costing spell as a reaction(from war caster) thus effectively casting 2 spells with levels per round plus 3 levelless spell. If you put Thief 17 to the mix(17 thief, 2 fighter, 1 caster), he will have an extra turn in his first turn of the combat, or in the first round of the combat, thus he will be able to effectively cast 3 or 41 action costing spells, and due having multiple turns, if anyone has less initiative than his second turn in first round, he will have another reaction granted by his second turn which will allow you another leveled spell as a reaction (When you take a reaction, you can't take another one until the start of your next turn....) So max spells: 4 1st level spells, 5 cantrips(of which 2 needs to be used as bonus action, you can conversely use 2 leveld spell as bonus action and use all cantrips as action costing spells if you have such spells), which means with proper build and buff(haste) you can cast 9 spells in a round.
(cantrip casting is spell casting as well, where does it state that you can can not cast cantrip with extra actions?)
"and it gains an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action."
Wands can still be used to release the spell strored inside, same goes for a magic scroll. But you are right about it which decreases the cantrip count not the leveled spell count as the leveled spell count (which is 4) does not rely on haste anyway.( a thief can use bonus action too for item interaction, which would actually modify what i ahve written above, increasing the leveled spell count to 6 rather than 4)
It does not say no casting allowed there tbh, it simply says, you can not cast a spell unless you can not cast it as part of attack action with a weapon, or as part of item interaction(item usage). This is how i interpret it, if the spell you cast says you can cast it as part of a weapon attack(dunno if such spell exist at the moment) you simply can cast it. So there is no "no casting allowed" written in the script...
Hm... I tend to diagree. Using spell scrolls is still a casting a spell action. And the rules text of e.g. a Rod of Ressurection says, that you can use an action to cast a spell.
In my opinion both cases do not fall under the use an object action.
Not to mention there are weapons which release stored spell upon hitting, you can use those too but, that is not the arguement and main point here...
What i try to point out is, even if you think inside the box, there are way around the rules, and they are not cheating, but simply rewards for creative thinking hidden within the rules.
Use an Object Action RAW: When an object requires your Action for its use, you take the Use an Object Action
Action granted by haste: That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action
DMG p.141 explicitly excludes magic item activation actions from Use an Object and also uses the rogue's Fast Hands as an example. So, no, no Rods or Spell Scrolls with Haste or as a rogue's bonus action.
Well then, we'll have that extra action for our sneak attack then sigh... and use our action surge for wand/rod, normal/default action for casting a spell, and use the bonus turn action to cast spell, bonus turns haste action to either use a dash/dis/hide or normal attack, and our 2 reactions to cast spell...which is still 4 spells(unless we have a weapon that casts spells upon hitting)...
Still 2 actions eligble to cast spells and 2 reactions eligible to cast spells since they are in different turns yet in same round, (assuming we have the slots) not to mention 2 bonus actions and the action that comes from action surge. We'll have to use 2 actions from haste for things like regular attacks and dashinG/disengaging as the extra movement from haste will work in tandem with dash or disengage. Eldritch spear and lance of lethargy makes cantrip eldritch blast more effective than level 1 spells in this build, so we can effectively drain the movement of multiple targets effectivelly stunning many targets in place and retreat at the same time.
OPs anwer, you can still cast multiple leveled spells with thief class and/or warcaster feat(as reaction), even without warcaster, there are spells like silvery barbs(if allowed in your game) or absorb elements which can be cast as a reaction thus not in your turn...So yes multiple spells can be cast within a round...Shield being a prime example of reaction based spells. I do advise polearm mastery/warcaster synergy too if you want to be able to cast 1 action costing spells as a reaction on your opponents turn.
Honestly i think action surge is overrated unlike thiefs final feature it is too limited(unless you are fighter with 4 attacks per turn). 2 level bladesinger, 1 fighter 17 level thief is kinda more fun, take a staff in your off hand which has spell focus feature(a specifically made one for that purpose, a magic staff with stored spells is even more appreciated) get polearm mastery and warcaster feats, even if its wielded in your offhand it triggers opportunity attack thus reaction spell casting from warcaster. 2 level bladesinger grants int as ac, and movement speed bonus also 3 spell slots(better get a feat that allows you free spell casting like fey touched too, metamagic feat is welcome as well), you are allowed 5-6 feats with this build... Fighter will give mariner style(or two weapon fighting for fun) which is while not so important still a good source of armor, you can take monk instead of a fighter level if you have high wis, and not planning to wear even light armor, that way your staff/spell focus will work as a dex based weapon too if need be, and you can kick stuff every now and then which is always handy. You can get 2 weapon feat for even more armor. You can get 17 thief with 3 sword rogue as well, this works better with point buy as 14 dex is easy(you ll get medium armor) and you can get two weapon fighting this way too, you can ignore class level race limitations on magical items so you can dual wield even holy sword meant for paladins, or moonblades meant for certain elven families with a staff of magery...assuming you can get/steal one. In Either combination thanks to thief's 17th level ability you'll be able to cast at least 2 spells in a round, and possibly 4 thanks to warcaster feat, even without action surge or haste.
Use an Object Action RAW: When an object requires your Action for its use, you take the Use an Object Action
Action granted by haste: That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action
DMG p.141 explicitly excludes magic item activation actions from Use an Object and also uses the rogue's Fast Hands as an example. So, no, no Rods or Spell Scrolls with Haste or as a rogue's bonus action.
Also, using a wand or rod to cast a spell is still casting a spell, which means it would continue to be restricted by the Bonus Action spell restriction:
This can obviously be different from an item with a magical function that doesn't specify it's casting a spell but as you noted: "If an item requires an action to activate, that action isn’t a function of the Use an Object action, so a feature such as the rogue’s Fast Hands can’t be used to activate the item." https://www.dndbeyond.com/sources/dmg/treasure#ActivatinganItem
"Thief's Reflexes" feature would still work since it's an additional turn in the first round, provided you didn't cast a bonus action spell in both turns and the ability to cast levelled spells as reactions has already been established (provided it's not part of the "ready action" and the reaction isn't activated on your turn such as featherfall or counterspell if their triggers occur during your turn). In fact, on the first "round" you could sort of have three reactions provided you aren't surprised. You can take a reaction before your first turn in the first round, you get your reaction back on your first turn so you can take it again after that turn and then a third time after your "Thief's Reflexes" turn. Obviously, these would require triggers for those reactions at the appropriate point before or between each turn.
If you can get Tiefling with spells Darkness and Hellish Rebuke, Warcaster feat, "Thief's Reflexes" with Rogue-Thief 17 and Action surge on a fighter 2 you could cast about 6 levelled spells in one "round" 1 x 1st reaction 2 x 1st turn with regular action and 1 action surge 1 x 2nd reaction 1 x 2nd turn (Thief's Reflexes) with regular action 1 x 3rd reaction
Obviously, if you used bonus action spells you could cast 5 levelled spells (3 x reaction, 2 x turn bonus actions) and 3 cantrips for a total of 8 spells including the 2 cantrips.
The spells could come from the Tiefling or another race with built in spells, magic items that can cast them, a feat, or class/subclass feature of some kind. Again, triggers required for the reactions at appropriate times, but if you don't use the bonus action spells, you can even take the reactions on you turn/s.
Really, it's a fairly ridiculous build (or way of using it) to take a 19/20th level character for the sake of a CHANCE of casting up to 6 levelled spells or 5 levelled spells and 3 cantrip spells in the first round considering they would all be fairly low level spells anyway and most of the things you might face at 19th/20th level. I guess magic item spells could be more appropriately levelled.
I am not really saying it's effective but tbh, using a modifief eldritch blast it can be made effective with 2 invocations feat, for the reaction trigger, getting a polearm master feat is my advice, as you can get a staff which also acts a spell focus, and use that to trigger opportunity attacks you need to shove targets further back.. So feats for such a build would be polearm master, warcaster, eldritch adept feat perhaps along with some warlock levels and perhaps metamagic, a rogue 17/ lock 3 or lock 1 fighter 2 can easily bombard multiple targets until their movement becomes 0, and he/she can even shove them even further back from great distances, if he invests at least 3 of his invocations on eldritch blast, in then simply escape either with stealth or invisibility. This character is effective, it is not a combat oriented character it is a thief, but it can still be of use in combat imho, and he has highly effective sneak attack as well, so along with eldritch blast he can actually deal some serious damage from 300 feet and simply run away. When i compare his first turn burst damage using a bow or a heavy crossbow from 300 range plus eldritch blasts(with 4x, 1d10 beams each can be sent to attack different targets, using the eldritch invocation you can slow each hit target by 10, and can be cast multiple times to effectively halt all targets) if character includes fighter level and if close quarter shooter is approved of, that fighting style gives +1 to attack rolls of all ranged attacks including spells(if it is not available in your game simply get anything you like, and use the action surge). Anyway your character can either get metamagic or sharpshooter, in first one you get to send 2 eldritch blasts that can shove the targets back and slow them as well, from 1200 feet, the second way allows for a massive sneak attack, followed by multiple eldritch blasts from 600 feet. Guiding bolt+ eldritch blast build is also possible with a stars druid, dragon thingie's saving throw bonus always helps anyway and at mid range this is still deadly enough even without distant or twinned spells. Again this build is not primarily a caster, just showing the verstality of the thief class.
(initially i was just trying to explain op how easy it is to cast 2 spells using war caster feat in tandem with polearm mastery, or with a thief at high levels sigh...)
(initially i was just trying to explain op how easy it is to cast 2 spells using war caster feat in tandem with polearm mastery, or with a thief at high levels sigh...)
I suspect you'll find that OP isn't still seeking an answer over 2 years later.
Never-the-less it was a good idea that spells in items might have helped, unfortunately not the case for he bonus-action restriction but I don't think anyone else had come up with it and it certainly helps with casting higher-level spells when you're taking up to 17 levels in Rogue-Thief.
Also, not sure by your wording of "Eldritch blast - Lance of Lethargy" but you can only slow one target by 10 feet once per turn "Once on each of your turns when you hit a creature". Although you might have been suggesting to slow 2 targets (another one on the extra turn created by Thief's Reflexes, although the first lance of lethargy would vanish after the thief's reflexes turn, which could matter if they take their turn after that one in the round or before your turn in the next round). Repelling Blast can be used multiple times. Remember that both of these note when you HIT and each ray of Eldritch blast is a separate roll and hit, even if it's a single casting, which is why hex's necrotic damage would stack with each hit because each one is it's own attack roll and separate hit or miss. https://twitter.com/JeremyECrawford/status/512337371979739136?ref_src=twsrc^tfw
Because of the RAW "your turn" obviously you couldn't use "Lance of Lethargy" evocation with Eldritch Blast in an off-turn reaction (and if it was on your turn it would be restricted by the "once" portion).
Once on each of your turns when you hit a creature with your Eldritch Blast, you can reduce that creature's speed by 10 feet until the end of your next turn.
In my turn i use eldritch blast once on 4 different targets( as i have four beams) effectively slowing down 4 creatures.
In my second turn like wise(from thief class)
I have two reactions that can be procced by polearm master/warcaster in this build. which allows me two more casting of eldritch blast.
with five eldritch blasts with repelling blast and 2 with lance of lethargy, i can put an effective distance between 4 creatures and my characters 50 feets plus my movement speedx2(due to extra turn)x2(due to dashes in bonus actions) and they will be moving 20 slower...
"once" i am using it once in my turn on four different creatures in the same instant with the same spell, another time in another turn of mine within the same round. Though you are right about that it's inneffective, repelling blast/eldritch spear seems to work better anyway, thank you for your time writing a detailed answer.
Once on each of your turns when you hit a creature with your Eldritch Blast, you can reduce that creature's speed by 10 feet until the end of your next turn.
In my turn i use eldritch blast once on 4 different targets( as i have four beams) effectively slowing down 4 creatures..
I don't know what your post has to do with casting multiple spells in a round, but you can only reduce one creature's speed per turn, not one per Eldritch Blast beam. You quoted it yourself: "Once on each of your turns..."
Once on each of your turns when you hit a creature with your Eldritch Blast, you can reduce that creature's speed by 10 feet until the end of your next turn.
In my turn i use eldritch blast once on 4 different targets( as i have four beams) effectively slowing down 4 creatures..
I don't know what your post has to do with casting multiple spells in a round, but you can only reduce one creature's speed per turn, not one per Eldritch Blast beam. You quoted it yourself: "Once on each of your turns..."
Previous post was in line with multiple targets and I just pointed out a mistake with the use of "Lance of Lethargy" so we've kind of hit a side discussion on that.
But this is correct. And I point again to the part about when you "HIT" as in pick a singular hit only once. A single Eldritch Blast at 17th level certainly has 4 beams but EACH beam counts as a separate attack roll and is a separate "HIT" so you only apply it ONCE per turn when you hit a creature. Figure out a way to cast it three times on a single turn and fire out 12 beams but you pick one of the beams that hits and apply it ONCE, on your turn, to that HIT. You don't get to apply Lance of Lethargy up to 4 times for each separate beam's potential hit. Again, this is supported by the use of Hex which would benefit from these separate hits by applying to each one. However Eldritch blast is hampered by it since it applies only ONCE on YOUR TURN when you HIT, not once when you cast Eldritch Blast for all 4 beams.
Wording is not "once per target" so even separating the beam to 4 targets doesn't allow you to apply the slow down to 4 targets and while it is a single casting of Eldritch Blast it's multiple attack rolls. I cast Eldritch blast and direct the beam at a target, I roll, I miss, I direct another at the same target, I roll, I hit and I apply "Lance of Lethargy" ONCE in my turn for that HIT. I direct the third beam at a different target, I roll, I hit but I can't apply "Lance of Lethargy" to that HIT because I already used it ONCE on my turn when I hit and it's not once on my turn when I cast. "Same spell" sure but different hits.
With "Thief's Reflexes" a creature cannot be under the effect of "Lance of Lethargy" twice because "That creature's speed by 10 feet until the end of your next turn. As you've noted, "Thief's Reflexes" gives you an extra turn in the round, so the first use of "Lance of Lethargy" would end with the "Thief's Reflexes" turn.
Action surge would only give you an extra casting on your turn, bonus action casting would be on your turn, reaction off-turn wouldn't be your turn and RAW it must be on your turn so this rules out any way I can immediately think of to have Eldritch Blast - Lance of Lethargy applying more than once to the same creature or different creatures at the same time when cast by one character (except for the brief period between a 2nd casting in Thief's Reflexes turn and the end of that turn).
Yep I agree with your point with Lethargy, as i have agreed before, repelling blast is the way to go, i have 2 invocations with this build anyway, as i have no level in warlock in most versions. Then again the build is only a longer range version of fist of unbroken air+ crusher monk(four elements), and a slower moving version, though it can use magic items and can sneak attack etc...Was just food for thought. Someone might need a build like that perhaps (i'd still prefer the monk tho or merge the two if possible). Anyway thanks for participating in brainstorming, have fun.
The question is "round" not turn, thus using the warcaster feat, yes you can as specific>general. A staff wielding sorcerer with polearm mastery and warcaster, can cast a 1 action spell as reaction(instead of an opportunity attack) to a target who/which enters his reach(which is his immideate hexes/squares, 5feet). Also, through the usage of metamagic(quicken spell) you can cast 1 leveled spell+ 1 cantrip in your own turn, and another leveled spell with the method written above, thus a total of 2 leveled spells plus a cantrip in 1 round. Unless i am wrong but this is how i interpreted RAW so far.
If you have haste, or action surge, this can be further increased(or the thief subclasses final feature which effectively allows you to play 2 turns thus 2 spells+ 2 cantrips + reaction spell due opportunity trigger of warcaster, a total of 5 spells in a round/first round of combat even without haste)
You have suggested haste twice now. How are you coming up with haste allowing additional spellcasting?
"Not all those who wander are lost"
It grants additional action, explanation about spell casting clearly says you can not cast more than 1 spells in your turn idd, but explanations take into account the base action count of a character class non modified by spells or spell like features, thus spells and spell like features become the "specific" in that regard.
A caster with no haste cast on him, no 2 levels of fighter, clearly has only 1 action per turn, thus it is clearly unable to cast 2 action costing spells(same goes for metamagic feat) thus you are right only cantrips can be used(unless you are using a charged wand to cast spells, as multiple item interactions is possible with multiple action granting spells and abilities)... So a fighter/mage with 3 actions(haste action surge can cast 1 single action spell plus 2 action costing cantrip, plus 1 bonus action costing cantrip, plus 1 action costing spell as a reaction(from war caster) thus effectively casting 2 spells with levels per round plus 3 levelless spell. If you put Thief 17 to the mix(17 thief, 2 fighter, 1 caster), he will have an extra turn in his first turn of the combat, or in the first round of the combat, thus he will be able to effectively cast 3 or 41 action costing spells, and due having multiple turns, if anyone has less initiative than his second turn in first round, he will have another reaction granted by his second turn which will allow you another leveled spell as a reaction (When you take a reaction, you can't take another one until the start of your next turn....) So max spells: 4 1st level spells, 5 cantrips(of which 2 needs to be used as bonus action, you can conversely use 2 leveld spell as bonus action and use all cantrips as action costing spells if you have such spells), which means with proper build and buff(haste) you can cast 9 spells in a round.
(cantrip casting is spell casting as well, where does it state that you can can not cast cantrip with extra actions?)
Haste only gives you a limited action:
"and it gains an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action."
No casting allowed here.
Wands can still be used to release the spell strored inside, same goes for a magic scroll. But you are right about it which decreases the cantrip count not the leveled spell count as the leveled spell count (which is 4) does not rely on haste anyway.( a thief can use bonus action too for item interaction, which would actually modify what i ahve written above, increasing the leveled spell count to 6 rather than 4)
It does not say no casting allowed there tbh, it simply says, you can not cast a spell unless you can not cast it as part of attack action with a weapon, or as part of item interaction(item usage). This is how i interpret it, if the spell you cast says you can cast it as part of a weapon attack(dunno if such spell exist at the moment) you simply can cast it. So there is no "no casting allowed" written in the script...
Rogue classes are there to break the laws, game rules are no exception, they skillfully evade longlasting game rules, legally...
Ah, ok now I understand.
"Not all those who wander are lost"
Hm... I tend to diagree. Using spell scrolls is still a casting a spell action. And the rules text of e.g. a Rod of Ressurection says, that you can use an action to cast a spell.
In my opinion both cases do not fall under the use an object action.
Use an Object Action RAW: When an object requires your Action for its use, you take the Use an Object Action
Action granted by haste: That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action
Not to mention there are weapons which release stored spell upon hitting, you can use those too but, that is not the arguement and main point here...
What i try to point out is, even if you think inside the box, there are way around the rules, and they are not cheating, but simply rewards for creative thinking hidden within the rules.
DMG p.141 explicitly excludes magic item activation actions from Use an Object and also uses the rogue's Fast Hands as an example. So, no, no Rods or Spell Scrolls with Haste or as a rogue's bonus action.
Well then, we'll have that extra action for our sneak attack then sigh... and use our action surge for wand/rod, normal/default action for casting a spell, and use the bonus turn action to cast spell, bonus turns haste action to either use a dash/dis/hide or normal attack, and our 2 reactions to cast spell...which is still 4 spells(unless we have a weapon that casts spells upon hitting)...
Still 2 actions eligble to cast spells and 2 reactions eligible to cast spells since they are in different turns yet in same round, (assuming we have the slots) not to mention 2 bonus actions and the action that comes from action surge. We'll have to use 2 actions from haste for things like regular attacks and dashinG/disengaging as the extra movement from haste will work in tandem with dash or disengage. Eldritch spear and lance of lethargy makes cantrip eldritch blast more effective than level 1 spells in this build, so we can effectively drain the movement of multiple targets effectivelly stunning many targets in place and retreat at the same time.
OPs anwer, you can still cast multiple leveled spells with thief class and/or warcaster feat(as reaction), even without warcaster, there are spells like silvery barbs(if allowed in your game) or absorb elements which can be cast as a reaction thus not in your turn...So yes multiple spells can be cast within a round...Shield being a prime example of reaction based spells. I do advise polearm mastery/warcaster synergy too if you want to be able to cast 1 action costing spells as a reaction on your opponents turn.
Honestly i think action surge is overrated unlike thiefs final feature it is too limited(unless you are fighter with 4 attacks per turn). 2 level bladesinger, 1 fighter 17 level thief is kinda more fun, take a staff in your off hand which has spell focus feature(a specifically made one for that purpose, a magic staff with stored spells is even more appreciated) get polearm mastery and warcaster feats, even if its wielded in your offhand it triggers opportunity attack thus reaction spell casting from warcaster. 2 level bladesinger grants int as ac, and movement speed bonus also 3 spell slots(better get a feat that allows you free spell casting like fey touched too, metamagic feat is welcome as well), you are allowed 5-6 feats with this build... Fighter will give mariner style(or two weapon fighting for fun) which is while not so important still a good source of armor, you can take monk instead of a fighter level if you have high wis, and not planning to wear even light armor, that way your staff/spell focus will work as a dex based weapon too if need be, and you can kick stuff every now and then which is always handy. You can get 2 weapon feat for even more armor. You can get 17 thief with 3 sword rogue as well, this works better with point buy as 14 dex is easy(you ll get medium armor) and you can get two weapon fighting this way too, you can ignore class level race limitations on magical items so you can dual wield even holy sword meant for paladins, or moonblades meant for certain elven families with a staff of magery...assuming you can get/steal one. In Either combination thanks to thief's 17th level ability you'll be able to cast at least 2 spells in a round, and possibly 4 thanks to warcaster feat, even without action surge or haste.
Also, using a wand or rod to cast a spell is still casting a spell, which means it would continue to be restricted by the Bonus Action spell restriction:
"Some magic items allow the user to cast a spell from the item."
https://www.dndbeyond.com/sources/dmg/treasure#Spells
This can obviously be different from an item with a magical function that doesn't specify it's casting a spell but as you noted:
"If an item requires an action to activate, that action isn’t a function of the Use an Object action, so a feature such as the rogue’s Fast Hands can’t be used to activate the item."
https://www.dndbeyond.com/sources/dmg/treasure#ActivatinganItem
"Thief's Reflexes" feature would still work since it's an additional turn in the first round, provided you didn't cast a bonus action spell in both turns and the ability to cast levelled spells as reactions has already been established (provided it's not part of the "ready action" and the reaction isn't activated on your turn such as featherfall or counterspell if their triggers occur during your turn). In fact, on the first "round" you could sort of have three reactions provided you aren't surprised. You can take a reaction before your first turn in the first round, you get your reaction back on your first turn so you can take it again after that turn and then a third time after your "Thief's Reflexes" turn. Obviously, these would require triggers for those reactions at the appropriate point before or between each turn.
If you can get Tiefling with spells Darkness and Hellish Rebuke, Warcaster feat, "Thief's Reflexes" with Rogue-Thief 17 and Action surge on a fighter 2 you could cast about 6 levelled spells in one "round"
1 x 1st reaction
2 x 1st turn with regular action and 1 action surge
1 x 2nd reaction
1 x 2nd turn (Thief's Reflexes) with regular action
1 x 3rd reaction
Obviously, if you used bonus action spells you could cast 5 levelled spells (3 x reaction, 2 x turn bonus actions) and 3 cantrips for a total of 8 spells including the 2 cantrips.
The spells could come from the Tiefling or another race with built in spells, magic items that can cast them, a feat, or class/subclass feature of some kind. Again, triggers required for the reactions at appropriate times, but if you don't use the bonus action spells, you can even take the reactions on you turn/s.
Really, it's a fairly ridiculous build (or way of using it) to take a 19/20th level character for the sake of a CHANCE of casting up to 6 levelled spells or 5 levelled spells and 3 cantrip spells in the first round considering they would all be fairly low level spells anyway and most of the things you might face at 19th/20th level. I guess magic item spells could be more appropriately levelled.
I am not really saying it's effective but tbh, using a modifief eldritch blast it can be made effective with 2 invocations feat, for the reaction trigger, getting a polearm master feat is my advice, as you can get a staff which also acts a spell focus, and use that to trigger opportunity attacks you need to shove targets further back.. So feats for such a build would be polearm master, warcaster, eldritch adept feat perhaps along with some warlock levels and perhaps metamagic, a rogue 17/ lock 3 or lock 1 fighter 2 can easily bombard multiple targets until their movement becomes 0, and he/she can even shove them even further back from great distances, if he invests at least 3 of his invocations on eldritch blast, in then simply escape either with stealth or invisibility. This character is effective, it is not a combat oriented character it is a thief, but it can still be of use in combat imho, and he has highly effective sneak attack as well, so along with eldritch blast he can actually deal some serious damage from 300 feet and simply run away. When i compare his first turn burst damage using a bow or a heavy crossbow from 300 range plus eldritch blasts(with 4x, 1d10 beams each can be sent to attack different targets, using the eldritch invocation you can slow each hit target by 10, and can be cast multiple times to effectively halt all targets) if character includes fighter level and if close quarter shooter is approved of, that fighting style gives +1 to attack rolls of all ranged attacks including spells(if it is not available in your game simply get anything you like, and use the action surge). Anyway your character can either get metamagic or sharpshooter, in first one you get to send 2 eldritch blasts that can shove the targets back and slow them as well, from 1200 feet, the second way allows for a massive sneak attack, followed by multiple eldritch blasts from 600 feet. Guiding bolt+ eldritch blast build is also possible with a stars druid, dragon thingie's saving throw bonus always helps anyway and at mid range this is still deadly enough even without distant or twinned spells. Again this build is not primarily a caster, just showing the verstality of the thief class.
(initially i was just trying to explain op how easy it is to cast 2 spells using war caster feat in tandem with polearm mastery, or with a thief at high levels sigh...)
I suspect you'll find that OP isn't still seeking an answer over 2 years later.
Never-the-less it was a good idea that spells in items might have helped, unfortunately not the case for he bonus-action restriction but I don't think anyone else had come up with it and it certainly helps with casting higher-level spells when you're taking up to 17 levels in Rogue-Thief.
Also, not sure by your wording of "Eldritch blast - Lance of Lethargy" but you can only slow one target by 10 feet once per turn "Once on each of your turns when you hit a creature". Although you might have been suggesting to slow 2 targets (another one on the extra turn created by Thief's Reflexes, although the first lance of lethargy would vanish after the thief's reflexes turn, which could matter if they take their turn after that one in the round or before your turn in the next round). Repelling Blast can be used multiple times. Remember that both of these note when you HIT and each ray of Eldritch blast is a separate roll and hit, even if it's a single casting, which is why hex's necrotic damage would stack with each hit because each one is it's own attack roll and separate hit or miss.
https://twitter.com/JeremyECrawford/status/512337371979739136?ref_src=twsrc^tfw
Because of the RAW "your turn" obviously you couldn't use "Lance of Lethargy" evocation with Eldritch Blast in an off-turn reaction (and if it was on your turn it would be restricted by the "once" portion).
Once on each of your turns when you hit a creature with your Eldritch Blast, you can reduce that creature's speed by 10 feet until the end of your next turn.
In my turn i use eldritch blast once on 4 different targets( as i have four beams) effectively slowing down 4 creatures.
In my second turn like wise(from thief class)
I have two reactions that can be procced by polearm master/warcaster in this build. which allows me two more casting of eldritch blast.
with five eldritch blasts with repelling blast and 2 with lance of lethargy, i can put an effective distance between 4 creatures and my characters 50 feets plus my movement speedx2(due to extra turn)x2(due to dashes in bonus actions) and they will be moving 20 slower...
"once" i am using it once in my turn on four different creatures in the same instant with the same spell, another time in another turn of mine within the same round. Though you are right about that it's inneffective, repelling blast/eldritch spear seems to work better anyway, thank you for your time writing a detailed answer.
I don't know what your post has to do with casting multiple spells in a round, but you can only reduce one creature's speed per turn, not one per Eldritch Blast beam. You quoted it yourself: "Once on each of your turns..."
Previous post was in line with multiple targets and I just pointed out a mistake with the use of "Lance of Lethargy" so we've kind of hit a side discussion on that.
But this is correct. And I point again to the part about when you "HIT" as in pick a singular hit only once. A single Eldritch Blast at 17th level certainly has 4 beams but EACH beam counts as a separate attack roll and is a separate "HIT" so you only apply it ONCE per turn when you hit a creature. Figure out a way to cast it three times on a single turn and fire out 12 beams but you pick one of the beams that hits and apply it ONCE, on your turn, to that HIT. You don't get to apply Lance of Lethargy up to 4 times for each separate beam's potential hit. Again, this is supported by the use of Hex which would benefit from these separate hits by applying to each one. However Eldritch blast is hampered by it since it applies only ONCE on YOUR TURN when you HIT, not once when you cast Eldritch Blast for all 4 beams.
Wording is not "once per target" so even separating the beam to 4 targets doesn't allow you to apply the slow down to 4 targets and while it is a single casting of Eldritch Blast it's multiple attack rolls. I cast Eldritch blast and direct the beam at a target, I roll, I miss, I direct another at the same target, I roll, I hit and I apply "Lance of Lethargy" ONCE in my turn for that HIT. I direct the third beam at a different target, I roll, I hit but I can't apply "Lance of Lethargy" to that HIT because I already used it ONCE on my turn when I hit and it's not once on my turn when I cast. "Same spell" sure but different hits.
With "Thief's Reflexes" a creature cannot be under the effect of "Lance of Lethargy" twice because "That creature's speed by 10 feet until the end of your next turn. As you've noted, "Thief's Reflexes" gives you an extra turn in the round, so the first use of "Lance of Lethargy" would end with the "Thief's Reflexes" turn.
Action surge would only give you an extra casting on your turn, bonus action casting would be on your turn, reaction off-turn wouldn't be your turn and RAW it must be on your turn so this rules out any way I can immediately think of to have Eldritch Blast - Lance of Lethargy applying more than once to the same creature or different creatures at the same time when cast by one character (except for the brief period between a 2nd casting in Thief's Reflexes turn and the end of that turn).
Yep I agree with your point with Lethargy, as i have agreed before, repelling blast is the way to go, i have 2 invocations with this build anyway, as i have no level in warlock in most versions. Then again the build is only a longer range version of fist of unbroken air+ crusher monk(four elements), and a slower moving version, though it can use magic items and can sneak attack etc...Was just food for thought. Someone might need a build like that perhaps (i'd still prefer the monk tho or merge the two if possible). Anyway thanks for participating in brainstorming, have fun.
And, how does "Counterspell" play into all this then?