Can I cast a bonus action spell and an at will spell like ability in the same round.
For instance, the warlock using Armor of Agathys, and the invocation Fiendish Vigor? Since Fiendish Vigor is at will of the spell False Life which is a first level spell but does not use a spell slot and it is at will I should as I am interpreting the rule be able to do so. Also each subsequent turn be able the cast it again and use my action to attack or even cast a cantrip as needed. This would maintain my temporary HP and thus keep the armor of Agathys up as well.
The rules reads:
Most spells require the Magic action to cast, but some spells require a Bonus Action, a Reaction, or 1 minute or more. A spell’s Casting Time entry specifies which of those is required.
One Spell with a Spell Slot per Turn
On a turn, you can expend only one spell slot to cast a spell. This rule means you can’t, for example, cast a spell with a spell slot using the Magic action and another one using a Bonus Action on the same turn.
Fiendish Vigor
Prerequisite: Level 2+ Warlock
You can cast False Life on yourself without expending a spell slot. When you cast the spell with this feature, you don’t roll the die for the Temporary Hit Points; you automatically get the highest number on the die.
It's not just at-will spells that do this either, spells given by feats or features that do not expend the spell slot can be cast like this.
So for Warlock, the Archfey Patron gives the character the ability to cast misty step a number of times equal to their charisma modifier without using a spell slot from the steps of the fey feature, using this to cast misty step and casting witch bolt with a spell slots on the same turn is also valid. However Archfey also gives the misty step spell anyways, if you had used all charges of steps of the fey, you can't use a spell slot to cast witchbolt and then use a spell slot to cast misty step, since that is two spell slots on the same turn.
Armor of Agathys now has a casting time of 1 Bonus Action, which is why JasonNatas brought it up in conjunction with False Life.
The actual problem with that scenario is that both spells grant Temporary Hit Points and those don't stack, and the new version isn't as clear on whether replacing Armor of Agathys's Temp HP would end it, but the principle is still correct. You could easily replace Armor of Agathys with Hex or some other Bonus Action spell though.
Can I cast a bonus action spell and an at will spell like ability in the same round.
For instance, the warlock using Armor of Agathys, and the invocation Fiendish Vigor? Since Fiendish Vigor is at will of the spell False Life which is a first level spell but does not use a spell slot and it is at will I should as I am interpreting the rule be able to do so. Also each subsequent turn be able the cast it again and use my action to attack or even cast a cantrip as needed. This would maintain my temporary HP and thus keep the armor of Agathys up as well.
The rules reads:
Most spells require the Magic action to cast, but some spells require a Bonus Action, a Reaction, or 1 minute or more. A spell’s Casting Time entry specifies which of those is required.
One Spell with a Spell Slot per Turn
On a turn, you can expend only one spell slot to cast a spell. This rule means you can’t, for example, cast a spell with a spell slot using the Magic action and another one using a Bonus Action on the same turn.
Fiendish Vigor
Prerequisite: Level 2+ Warlock
You can cast False Life on yourself without expending a spell slot. When you cast the spell with this feature, you don’t roll the die for the Temporary Hit Points; you automatically get the highest number on the die.
Yes. You understand the rule correctly.
It's not just at-will spells that do this either, spells given by feats or features that do not expend the spell slot can be cast like this.
So for Warlock, the Archfey Patron gives the character the ability to cast misty step a number of times equal to their charisma modifier without using a spell slot from the steps of the fey feature, using this to cast misty step and casting witch bolt with a spell slots on the same turn is also valid. However Archfey also gives the misty step spell anyways, if you had used all charges of steps of the fey, you can't use a spell slot to cast witchbolt and then use a spell slot to cast misty step, since that is two spell slots on the same turn.
No, false life is an action.
You are winning the game. Good job! Oh wait...
But Armor of Agathys isn't (any more)
Anyway, it's just an example. (Which is good, because they're both temp HP effects, which don't stack)
Armor of Agathys now has a casting time of 1 Bonus Action, which is why JasonNatas brought it up in conjunction with False Life.
The actual problem with that scenario is that both spells grant Temporary Hit Points and those don't stack, and the new version isn't as clear on whether replacing Armor of Agathys's Temp HP would end it, but the principle is still correct. You could easily replace Armor of Agathys with Hex or some other Bonus Action spell though.
The Forum Infestation (TM)