I've looked but cannot seem to find a ruling on this. There are probably other situations where this can occur but I'll use my current one as an example.
I have a Warlock (level 7) with the Lance of Lethargy invocation and the spells Eldritch Blast and Sickening Radiance.
If I have a creature in the area of SR it has its movement speed reduced by half. If I hit it with EB and apply lance its movement speed is also reduced by 10 until my next turn. We'll say the creature has base movement speed of 30. What order would the reductions be applied in?
If you apply the Sickening Radiance reduction first, the target would have (30/2)-10 = 5 feet of movement. But if Lance of Lethargy is applied first it would have ((30-10)/2) = 10 feet of movement. Anyone know a ruling on this?
Apply the penalties in the order in which they occur. If they're already in the aura before getting hit by the eldritch blast, the aura applies first. If they're hit by eldritch blast and then enter the aura, Lance of Lethargy applies first.
I would apply in the order received, but if they happened to be hit at the same time (if that's possible) i'd use PEMDAS so the halving would occur first
The rules don't give an order of operations for general bonuses, so officially it's the DM's call. That said, applying multipliers last is the way to go in my opinion:
It's consistent with damage resistance, and the rules shouldn't be complicated more than necessary.
With respect to SagaTympana, there's no good reason why applying two effects in different orders should give different results, and running things that way adds needless bookkeeping. You normally get the same result no matter which order bonuses and penalties are applied; +2 bonus and a +3 bonus always adds up to +5.
Applying multipliers first is broken, which is why damage resistance doesn't work that way. A +/- 10 is huge if your speed has been pre-halved, and negligible if it's been pre-doubled. Pre-halving makes it a little too easy to bring a speed down to 0 with cantrips (e.g. Lance of Lethargy + Ray of Frost). Having 0 speed has knock-on effects like canceling the benefits of the Dodge action or causing flying creatures to fall if they can't hover.
Applying multipliers last keeps the effects of modifiers proportional. A -10 penalty to a base speed of 30 reduces their final speed by 1/3 regardless of whether their speed's being doubled, halved or neither. Likewise, applying a halving or doubling effect gives you half or double whatever speed they already had regardless of their fixed modifiers, as opposed to getting weird results like 30 - 10 = 20 but 30/2 - 10 = 5. You get consistent effects and intuitive results no matter how they're combined or in what order.
I think there might be precedence somewhere in the rules for "target chooses" (I could be thinking of a different game). Either way, that is a good option too.
Xanathar's Guide to Everything adds that as an optional rule for resolving effects that would trigger simultaneously, e.g. two effects that apply at the start/end of your turn.
I know this has been a while, but a great slow combo can be found in one subclass of Warlock, which is made stronger by using the expanded rules subclass with the new 2024 Warlock class options:
You need: 5 Levels of Warlock Fathomless Subclass Lance of Lethargy Invocation (previously usable only with Eldritch Blast, which was good enough, but is now stronger with the option to put on another cantrip), now applied to... Ray of Frost Cantrip and the reason for minimum 5 levels is Summon Shadowspawn (you will be using the Despair Option for this) Which synergizes with your Tentacles of the Deep Subclass Feature
How the combo works: You summon the Despair Shadowspawn and command it to attack on its turn (commanding it is a free action, summoning it will be your action for this turn) Bonus Action summon the Tentacles of the Deep behind the foe (It gets to take advantage of flanking, and can hit as part of the bonus action of being summoned), which will hit for 1d8 Cold and reduce the Opponent's speed by 10 Feet til the start of your next turn. Take cover (this is just so the foe can't target you and try to break your concentration, forcing them to deal with only the Shadowspawn or your other allies) The Shadowspawn does damage (this is less important, but still, damage is damage) Opponent starts its turn within 5' of the Shadowspawn, further reducing their speed by an additional 20' (this will happen at the start of their turn as long as they are within 5' of the Despair Shadowspawn, this means for most foes, they are -30' to movement, which is most creatures movement, but we're not done) Even if the foe has more movement, their speed is greatly reduced, which should mean you can have the Shadowspawn dash to get back in range if they somehow had 40 feet of movement left (yeah, the Shadowspawn has 40 of base movement, so you can have it pursue foes that somehow still had movement after losing 30, plus the tentacles can still be moved 30 feet as a bonus action) No matter what, now that the Despair is out, you can now just bonus action attack with the Tentacles, and then Ray of Frost with Lance of Lethargy as your action on subsequent turns, popping out of cover to shoot, then ducking back behind cover... the Ray of Frost reduces speed by another 10 feet, and the Lance of Lethargy a further 10 feet, that is now -50 feet of movement a turn stolen from foes, and you can just lock a foe down this way, round after round for a minute, using your action to shoot, bonus action to hit them with the tentacles, free action to command the Shadowspawn, and movement to keep yourself behind full cover when not blasting them to eliminate that pesky chance of them targeting you. Add in allies with Longbows or Light Crossbows, or even Javalins or Slings, adding the Slow Weapon Mastery, and the foe is even more locked down.
She Shadowspawn is even good for multiple foes, as it affects everyone within a 5' radius around it, can be targeted by Enlarge/Reduce for even bigger area of affect, and while you'd surrender the added -10 feet from Ray of Frost itself, if you want to slow groups, Lance of Lethargy with Eldritch Blast would allow you to lockdown two or three foes with a variation at level 5 and more as you level up, since you can have the tentacles slowing one foe, and split your eldritch blast on other foes, reducing all by 30' a turn around the Shadowspawn...
NOTE: Prior to 2024 rules, the last paragraph was still how you could reduce a foe by 40' a round or multiple by 30', 2024 just lets other allies add Slow for more reduction, and allowed you to use Ray of Frost with the Lance of Lethargy for added individual slow focus. Someone still playing 2014 Expanded Rules can Summon the Despair Shadowspawn, Summon the Tentacles of the Deep, slow for 30' on first round, and slow for single target 40' or multiple 30's on subsequent rounds (or one for 40 and others for 30). So this combo didn't just become available with 2024, it just became Stronger with 2024's optional backwards compatibility possibilities.
I've looked but cannot seem to find a ruling on this. There are probably other situations where this can occur but I'll use my current one as an example.
I have a Warlock (level 7) with the Lance of Lethargy invocation and the spells Eldritch Blast and Sickening Radiance.
If I have a creature in the area of SR it has its movement speed reduced by half. If I hit it with EB and apply lance its movement speed is also reduced by 10 until my next turn. We'll say the creature has base movement speed of 30. What order would the reductions be applied in?
If you apply the Sickening Radiance reduction first, the target would have (30/2)-10 = 5 feet of movement. But if Lance of Lethargy is applied first it would have ((30-10)/2) = 10 feet of movement. Anyone know a ruling on this?
Apply the penalties in the order in which they occur. If they're already in the aura before getting hit by the eldritch blast, the aura applies first. If they're hit by eldritch blast and then enter the aura, Lance of Lethargy applies first.
As always, just do what the DM says.
If it were me, I'd apply the speed loss from exhaustion first, then lance of lethargy, so 5 ft.
I would apply in the order received, but if they happened to be hit at the same time (if that's possible) i'd use PEMDAS so the halving would occur first
The rules don't give an order of operations for general bonuses, so officially it's the DM's call. That said, applying multipliers last is the way to go in my opinion:
The Forum Infestation (TM)
I think there might be precedence somewhere in the rules for "target chooses" (I could be thinking of a different game). Either way, that is a good option too.
Xanathar's Guide to Everything adds that as an optional rule for resolving effects that would trigger simultaneously, e.g. two effects that apply at the start/end of your turn.
The Forum Infestation (TM)
I know this has been a while, but a great slow combo can be found in one subclass of Warlock, which is made stronger by using the expanded rules subclass with the new 2024 Warlock class options:
You need:
5 Levels of Warlock
Fathomless Subclass
Lance of Lethargy Invocation (previously usable only with Eldritch Blast, which was good enough, but is now stronger with the option to put on another cantrip), now applied to...
Ray of Frost Cantrip
and the reason for minimum 5 levels is
Summon Shadowspawn (you will be using the Despair Option for this)
Which synergizes with your Tentacles of the Deep Subclass Feature
How the combo works:
You summon the Despair Shadowspawn and command it to attack on its turn (commanding it is a free action, summoning it will be your action for this turn)
Bonus Action summon the Tentacles of the Deep behind the foe (It gets to take advantage of flanking, and can hit as part of the bonus action of being summoned), which will hit for 1d8 Cold and reduce the Opponent's speed by 10 Feet til the start of your next turn.
Take cover (this is just so the foe can't target you and try to break your concentration, forcing them to deal with only the Shadowspawn or your other allies)
The Shadowspawn does damage (this is less important, but still, damage is damage)
Opponent starts its turn within 5' of the Shadowspawn, further reducing their speed by an additional 20' (this will happen at the start of their turn as long as they are within 5' of the Despair Shadowspawn, this means for most foes, they are -30' to movement, which is most creatures movement, but we're not done)
Even if the foe has more movement, their speed is greatly reduced, which should mean you can have the Shadowspawn dash to get back in range if they somehow had 40 feet of movement left (yeah, the Shadowspawn has 40 of base movement, so you can have it pursue foes that somehow still had movement after losing 30, plus the tentacles can still be moved 30 feet as a bonus action)
No matter what, now that the Despair is out, you can now just bonus action attack with the Tentacles, and then Ray of Frost with Lance of Lethargy as your action on subsequent turns, popping out of cover to shoot, then ducking back behind cover... the Ray of Frost reduces speed by another 10 feet, and the Lance of Lethargy a further 10 feet, that is now -50 feet of movement a turn stolen from foes, and you can just lock a foe down this way, round after round for a minute, using your action to shoot, bonus action to hit them with the tentacles, free action to command the Shadowspawn, and movement to keep yourself behind full cover when not blasting them to eliminate that pesky chance of them targeting you.
Add in allies with Longbows or Light Crossbows, or even Javalins or Slings, adding the Slow Weapon Mastery, and the foe is even more locked down.
She Shadowspawn is even good for multiple foes, as it affects everyone within a 5' radius around it, can be targeted by Enlarge/Reduce for even bigger area of affect, and while you'd surrender the added -10 feet from Ray of Frost itself, if you want to slow groups, Lance of Lethargy with Eldritch Blast would allow you to lockdown two or three foes with a variation at level 5 and more as you level up, since you can have the tentacles slowing one foe, and split your eldritch blast on other foes, reducing all by 30' a turn around the Shadowspawn...
NOTE: Prior to 2024 rules, the last paragraph was still how you could reduce a foe by 40' a round or multiple by 30', 2024 just lets other allies add Slow for more reduction, and allowed you to use Ray of Frost with the Lance of Lethargy for added individual slow focus. Someone still playing 2014 Expanded Rules can Summon the Despair Shadowspawn, Summon the Tentacles of the Deep, slow for 30' on first round, and slow for single target 40' or multiple 30's on subsequent rounds (or one for 40 and others for 30). So this combo didn't just become available with 2024, it just became Stronger with 2024's optional backwards compatibility possibilities.