Not to be "that" person, but WoW has an ability (I know of only one at least) that does something like this. The Death Knight's Soul Reaper ability, you appy it and it sticks a 5s debuff, if they die within that 5s the Death Knight gets a 3s 5% haste and movespeed boost, if they don't the debuff wearing off the enemy while it's still alive causes them to take X amount of damage.
Is that something along the lines of what you were thinking?