Angel of Roy's Destruction

({p/c} can be paid with either {1}or 2 life or a blood sacrifice to the gods of WoTC.)
Flying, double strike
Whenever a creature you control deals
combat damage to a player, or just exists, you
and that player each gain that much life.
At the beginning of your end step, if you
have at least 15 life more than your starting
life total, or if you don't, each player named Roy
loses the game.