More background system

Hey, I am attempting to make a “good” multiplayer boss battle. I am trying to make diffrent attacks the lower the boss gets. Right now there are 3 ways to track, health, time, and score. Right now health is being tracked to tell how many players are alive, and score and time will be attacks. But if anyone knows how to have more values for attacks or say “your making this way to hard on yourself.” It would be appreciated.