Ask the sage

Ricky asked the Dungeons & Dragons sage:

If a character has polymorphed into a hydra and loses a head, what happens when he returns to his normal form?

Here’s my answer:

Ricky, when you come to a question like this—that the rules do not explicitly cover—there are three methods the Dungeon Master may use to answer this question:

1. What would be the most fun?
2. What makes for the best story?
3. Let the dice decide.

Most importantly, however, is to recognize that this is the key ingredient of games like Dungeons & Dragons: They have a human referee (Dungeon Master, Game Master, &c.) who serves as a living rulebook. As was written in the third of the original booklets...

In this light, we urge you to refrain from writing for rule interpretations or the like unless you are absolutely at a loss, for everything herein is fantastic, and the best way is to decide how you would like it to be, and then make it just that way!

...why have us do any more of your imagining for you?

This is why Gary Gygax could write...

What I think isn’t important. It is what your DM decides that is.

I will, however, note that a wise DM seeks & considers the advice of his players.