Our group's paladin/warlock (multiclass) was wondering about the following scenario. The paladin/warlock uses his reaction to use the Tomb of Levistus eldritch invocation (from Xanathar's Guide to Everything, p. 57):
As a reaction when you take damage, you can entomb yourself in ice, which melts away at the end of your next turn. You gain 10 temporary hit points per warlock level, which take as much of the triggering damage as possible. Immediately after you take the damage, you gain vulnerability to fire damage, your speed is reduced to 0, and you are incapacitated. These effects, including any remaining temporary hit points, all end when the ice melts.
Then my character, our group's sorcerer, proceeded to cast polymorph on him immediately following. Does it break or melt the ice, immediately ending the effects of the invocation?
We do not know if there is an official answer to this, or how we are going to treat it just yet. When I cast polymorph on our barbarian who was raging to turn him into a giant ape, it was ruled that it ended his rage under the idea that polymorph changes your stat blocks and therefore ends class features, which include a warlock's invocations. We're not quite sure what to do here.
If a character is polymorphed after using Tomb of Levistus, what happens? Does the ice break/go away because the new form can no longer use the invocation?