Some creatures have an ability that lets them polymorph, such as the Couatl's Change Shape action. I am wondering if this ability could be used again whenever the form is dropped to give the creature a massive effective health pool.

For example, if the Couatl used their action to Change Shape and become a Veteran, then was hit for enough damage to kill the polymorphed form, could it then re-use the Change Shape ability to transform into a fully healed Veteran once more?


The creature's HP is not affected by Change Shape

You have a misconception in this question. You are assuming that the Couatl's HP changes when using its Change Shape ability but this is not true.

Note that the ability says:

In a new form, the couatl retains its game statistics

After this quote, some exceptions are included but not HP. This means that its HP remains the same as it was. Changing Shape or going back to its original form does not affect its current HP in any way.

This is different from the spell polymorph, which does affect the creature's HP in the way you describe, but most (if not all) creatures that have some form of at-will Shapechanging ability work the same way as the Couatl regarding their HP. Take the example of the Oni which has also been asked about here.

So yes, they can spam their Change Shape, but since it does not affect HP, it is not really a problem.

  • 2
    \$\begingroup\$ It might be worth addressing the general case, presumably by saying "it depends on the monster's trait and whether it says it changes their HP". \$\endgroup\$ – V2Blast Mar 2 '19 at 19:10
  • \$\begingroup\$ @V2Blast Sure but I could not find a shapechanger monster which does change HP when changing for contrast. \$\endgroup\$ – Sdjz Mar 2 '19 at 19:26
  • \$\begingroup\$ In that case, it's worth noting that from what you've seen, other monsters' Change Shape traits work the same way. :) \$\endgroup\$ – V2Blast Mar 2 '19 at 20:02
  • \$\begingroup\$ What about an evil Druid? It seems that the Druid's ability to polymorph give them HP in the new form, right? \$\endgroup\$ – Alexis Wilke Mar 3 '19 at 0:53
  • \$\begingroup\$ A PC's Beast shape would do that, but according to the MM, a basic NPC druid does not have Beast Shape/Change Shape (p. 346). The Archdruid in Volo's does, but it reads the same as a monster's Change Shape, including "retains its game statistics" (p. 210). \$\endgroup\$ – MissMisinformation Mar 3 '19 at 1:14

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