Does True Polymorph end if the CR requirement is no longer met?

Question

True polymorph is a spell that allows for the transformation of a creature into another of equal or lower CR.

Does this spell end if the CR of the original creature is reduced after the true polymorph spell is cast?

One way this could be accomplished is through these steps:

1. Druid casts animal shapes on a creature to transform a hawk into a giant scorpion
2. Wizard casts true polymorph to transform the giant scorpion into an owlbear
3. Druid stops concentrating on animal shapes (meaning the creature is now a hawk true polymorphed into an owlbear)

Does true polymorph end or does something else occur that prevents this effect? Does it make a difference whether or not true polymorh becomes permanent first?

Answer 1

True Polymorph does not end

This is not an issue of targeting

The targeting requirement of true polymorph is as follows:

Choose one creature or nonmagical object you can see within range. You transform the creature into a different creature...

The only targeting requirements specified by the spell are a creature or a nonmagical object. Both a hawk and a giant scorpion are both creatures so the targeting requirement of the spell is met on casting and after.

CR is not a requirement to keep the spell running

Later in the description it describes more about the effect of the spell:

If you turn a creature into another kind of creature, the new form can be any kind you choose whose challenge rating is equal to or less than the target's...

This is a one-time effect not a continuous condition of the spell. At the time you cast the spell the target was a giant scorpion with CR 3. That means that you can choose any form that is CR 3 or lower.

When the druid stops concentrating on animal shapes they have not changed anything about the situation or any statistics of the creature. When the spell ends the creature has already been transformed into an owlbear with all the statistics of an owlbear. The fact that the owlbear will transform back into a hawk if the spell ends is irrelevant to whether or not true polymorph keeps going.

Thus, true polymorph keeps going because nothing has changed and nothing about the spell's conditions has been violated in any way.

Answer 2

No, True Polymorph does not end.

Sage Advice has had several other questions regarding spells persisting if the target is changed and no longer meets the requirements of the spell. For example, if the target of a Charm Person spell is changed to a Beast.

Relevant Sage Advice

Does Charm Person ends if polymorph is cast on the charmed humanoid, changing its type to beast?

Mike Mearls: Nope, restriction applies to targeting - sticks after successful cast #wotcstaff

The target was a valid target at the time of the spell being cast. Modifying the target later does not retroactively undo the original spell.

Answer 3

After reading the spell descriptions carefully, I think the two spells are diametrically opposed. Animal Shapes states:

The transformation lasts for the Duration for each target, or until the target drops to 0 hit points or dies.

So, say you change a creature from shape Y into shape X. The transformation, shape X, will last until one of these conditions is met: The caster uses an action to choose a new form, the caster stops concentrating, 24 hours go by, the target drops to 0 hit points, or the target dies.

True Polymorph transforms the target into something else. Lets call it shape Z. This is a different transformation. That is a direct contradiction with what Animal Shapes' spell description states.

The effects of different spells add together while the duration of those spells overlap.

(See: Combined magical effects)

The two spell's effects are added together, but not compatible. Thus, the two spells are in conflict.

I think this is an accurate reading of the spell descriptions. I also think this makes sense thematically. If one spell is focused on maintaining shape X, it would be in conflict with a spell focused on maintaining shape Z.

So where does that leave us? I think the higher level spell wins (or you trigger a conflict on a tie), but I only have instinct and flimsy evidence to back that assertion up.

So that leaves us with three possibilities to solve the conflict:

1. True Polymorph wins the contest and cancels Animal Shapes on the target.

   1A. True Polymorph uses the Animal Shapes form's CR for its restriction on the new form. That means that form Z can have a CR of up to form X's CR.

   1B. True Polymorph uses the target's original CR. That means that form Z can have a CR of up to form Y's CR.

2. Animal Shapes wins the contest (for some reason) and True Polymorph is canceled. This means that shape X is maintained as described in Animal Shapes and True Polymorph has no effect.

3. The two spells conflict and nullify each other. That means the target reverts to shape Y and both spells end.

Any of these options would solve the paradox, but I don't see options 2 or 3 as being very likely. So, option 1. I believe, that rules as written, 1A is more technically correct. Until True Polymorph's transform is applied, the creature has shape X and thus shape X is used for True Polymorph's restrictions.

That said, as a DM, I would enforce 1B. I believe that permanently increasing a creature's CR using True Polymorph is not something that should be possible.

Answer 4

True polymorph remains.

Also the new owlbear remains an owlbear. From the moment true polymorph was cast the druid can no longer influence the creature through a spell cast before true polymorph.

This works like all shape-shifting spells. An alter self becomes irrelevant when you get polymorphed into something completely different. Same with animal shapes. The owlbear is now a real owlbear, and that's all it is until something else is cast on it.