Is it possible to use a reaction from your class when your polymorphed form is reduced to 0 hit points and the excess carries over to you?

For example, let's say you're playing a rogue and your friendly wizard polymorphs you into a giant ape. Battles continues, and after a failed dexterity saving throw, you take 50 damage. Since your giant ape only had 10 hp left, you take 40 hp to your rogue health. Since you're not under the Polymorph spell, can you use your reaction to do Uncanny Dodge and only take half of the 40 damage you're taking?

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    \$\begingroup\$ You seem to be using “trample” in the Magic: The Gathering sense—which is not really super-clear to me, and I’m familiar with the game. In the context of that game (and monsters “trampling over” some defender to reach the enemy wizard), the word makes sense, but divorced from that context, it doesn’t quite work, that’s not quite what “trample” means. I recommend considering something like “carry over” or something. \$\endgroup\$
    – KRyan
    May 21, 2021 at 3:37
  • \$\begingroup\$ @KRyan makes sense, I use the first term that came to my mind and couldn't find another way to express it. Excess and carry over will do the trick ! \$\endgroup\$ May 21, 2021 at 14:53
  • \$\begingroup\$ Is your question specifically about Uncanny Dodge, or more generally about reactions? Your question title implies the latter, but the end of your question and the currently accepted answer imply the former. \$\endgroup\$
    – RHS
    May 21, 2021 at 15:24
  • \$\begingroup\$ A better example might be Absorb Elements, which confers resistance against the triggering damage. \$\endgroup\$ May 21, 2021 at 21:25

2 Answers 2


No, you take the full damage

Uncanny Dodge's trigger is "when an attacker that you can see hits you with an attack", and the result is "you can use your reaction to halve the attack's damage against you". By the time you've taken some of the damage, the trigger has passed.

From a logical perspective this makes sense too; someone just smacked a giant ape hard. The giant ape has no special dodging ability. Dodging as you get smacked back into a human when they already hit you makes no sense.

  • \$\begingroup\$ I agree but I'm talking about using reactions, so dodging is not a good comparison. I'll update the question. \$\endgroup\$ May 21, 2021 at 3:27
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    \$\begingroup\$ @RegularNormalDayGuy: I referred to "dodging" because the feature is called "uncanny dodge"; that was just the "logical (non-game rules) perspective". The rules answer isn't changed because you call it a "reaction" vs. dodging; if the ability is triggered on being hit, it's too late to apply the ability by the time the damage rolls over to your natural form. It would also be too late if the ability triggered when you take damage from "an attack", because the attack's damage has already begun applying before you're eligible to use the ability; you can't retroactively halve it. \$\endgroup\$ May 21, 2021 at 10:42

It depends on the reaction.

The specific language of the trigger and the timing of the reaction in question are important to answering this question.

If you have a reaction that happens in response to to taking damage, like say the hellish rebuke spell, then yes, if your polymorphed form is reduced to zero HP and you revert to normal, taking some overage damage in the process, that damage you took can trigger a reaction that is now available but wasn't when you were in animal form.

However, if (as in your example) un-transforming enables a reaction that responds to taking a hit, such as Uncanny Dodge ("when an attacker that you can see hits you with an attack") or the shield spell ("when you are hit by an attack"), you can't use that. It's too late; the attack already hit, damage has already been rolled and applied. The trigger passed while the reaction was unavailable.

  • \$\begingroup\$ I agree and would like to back it up with another example: If a druid in wild shape falls, and while falling transforms back, they should be allowed to use the trigger of "Feather Fall" which says "when you or a creature within 60 feet of you falls". The falling started when the trigger was not available, but the trigger became available before the falling was over, so I think Feather Fall should be (allowed to be) triggered after Wild Shape was reverted. \$\endgroup\$
    – RHS
    May 21, 2021 at 15:20

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