Chamber Sentry
{X}
Artifact Creature -- Construct
0/0
~this~ enters with a +1/+1 counter on it for each color of mana spent to cast it.
{X}, {T}, Remove X +1/+1 counters from ~this~: It deals X damage to any target.
{W}{U}{B}{R}{G}: Return ~this~ from your graveyard to your hand.