Sea-Dasher Octopus

Mutate's whole reward hinges on stapling a keyword-loaded creature onto a body that already wants to attack, and this is the octopus that most cleanly delivers on that premise. Cast for its full cost, it is a flash 2/2 that draws you a card whenever it connects, the kind of tempo tool blue has always paid a premium for. Cast for its mutate cost, it becomes far nastier: for two mana at instant speed you can graft the draw trigger, plus the evasion or trample of whatever it merges with, onto a creature that has already resolved, dodging the summoning-sickness tax that usually keeps a fresh attacker home for a turn. The ninjutsu comparison is instructive: both mechanics reward getting a body into the red zone and then upgrading it mid-tempo, but where ninjas swap in and bounce the original to hand, mutate stacks into a single pile that shares every ability at once. That flash-plus-mutate pairing is the singular thing here. It lets you hold the octopus as a combat trick, an end-of-turn ambush blocker, or a surprise upgrade that turns a stalled ground creature into a repeatable card engine at the moment your opponent has committed to a board they can no longer profitably block into. The catch that keeps it honest: the pile is one permanent, so a single removal spell answers the whole stack, engine and all.