Interesting concept that's definitely hard to execute well. Well done!
The game's mechanics were pretty tough to grasp initially, probably because I didn't really understand the goal of the game ("I killed or possessed everyone, how come I didn't win the level?"). The learning process would have been much smoother, for me personally at least, if I were told at the very beginning that my goal is to possess the boss, not kill him.
Once I understood the goals and mechanics, the game was pretty fun. I really enjoyed the approach you needed take to solve the last level, nice puzzle design on that one :)
I'm curios why you chose to add the "Follow" mechanic. The game would probably have been easier to understand without it, since it's not immediately evident that you can only affect the neighbors of the selected minion, and as far as I understood things, your available actions (or their chances of success) don't depend on the minion you currently have selected.
Nice concept, nice puzzles and the game fits the theme well. Good job!