Making a adrenaline system?

If i’m trying to make a adrenaline system where if your health goes down to 10% you will gain adrenaline and if you die while your adrenaline is at 100% you will come back to life how would i do that? also this includes no armor

Whenever you lose health, check if it fell below MaxHealth0.1, *start accumulating Adrenaline in a variable (timer event perhaps). On death, check if Adrenaline is at max value; if it is, don’t kill the player, grant them extra health or invincibility.

This includes no armor (whatever that means)