Curse of Mortality I

Tap Target creature with power equal to your Devotion to blue. put {x} lifespan conters on it, where {x} is your devotion to balck. Each time that crature atack, block or use it`s activate effect remuve one counter, when the creature runs out of counters destroy it, dealing damge equal to the amount of lifespan counters to the creature owner. you gain lifes equal to the damage del thes way.