I gave the my enemies HP, but they still die instantly. Why?

There are three ways that an enemy can die:

1. It can run out of HP (either by being attacked, attacking itself, or by having 0 HP in the first place)
2. It can have the "Die without Boss" bitset on, and there is no enemy with the "Boss" bitset on.
3. If all the live enemies have the "untargetable by hero" bitset on, the battle ends.

If you're sure you gave your enemies HP, and you're sure you didn't give them the "Die without Boss" bitset, then please report a bug to let us know.