Board Thread:General Discussion/@comment-32237043-20160626014030/@comment-86484-20161214162830

It says monsters' bodies are attuned to their SOUL. How exactly the connection works is up to interpretation, but Mettaton's attack was 10 in one battle and 8 in another and he had no intention to kill in either, so it's more than just will to kill or lack thereof. Anyway, my point is that stats can change. What exactly triggers the changes is debatable. It has something to do with the monster's SOUL, but that's pretty vague. My best bet is emotions because emotions change over time and the stats shown in the game seem to match the monsters' emotions, but again, that's subjective. And the will to kill is a result of emotions too.