Shiragon, Mind's Sword

Shiragon, Mind's Sword enters the battlefield
with a -1/-1 counter on it.
At the beginning of your upkeep, you may pay
{u}{u}{b}. If you do, put a +1/+1 counter on
Shiragon, Mind's Sword.
Whenever a creature you control dies, you may
sacrifice Shiragon. If you do, create a blue 0/0
Minion creature token, the put X +1/+1 counters
on it, where X is Shiragon's power.