I am making a boss battle, and the boss has a few different stages already implemented, I just need a detector to tell the stages when to activate. To activate the final stage, I want the mob to have less than 20 half hearts, and I try to test that with this command:
However it does not seem to find the mob. In case I'm changing the wrong thing, this post refers to the only other variable that could be affected/affect the mob. Did I make an error in the syntax?