Yes, sorry. That was excessively brief of me.
I ran the game two times. The first time, the possession button either didn't do anything, or only teleported the player to the target enemy without possessing them. Both times the player was immortal and enemies would not attack each more than once (other than the archer). for ~3s after starting the second time blue hearts appeared above the red ones. I assume that was supposed to be the possessed creature's health bar, but they never appeared at any other point, even when possessing a target.
Best of luck.