Mutable Rat Swarm

Deathtouch
{b}: Regenerate Mutable Rat Swarm.
{u} Choose one - Mutable Rat Swarm is unblockable this turn; or until end of turn Mutable Rat Swarm becomes a copy of target creature except it has "{b}: Regenerate this creature." and is a black and blue Rat in addition to it's other colors and types. Activate this ability only once each turn.