Essence Symbiote

Mutate was an awkward mechanic to build payoffs for, because the reward has to attach to an action, not a permanent: you never cast a spell called "mutate," you glue a nonhuman creature onto another and keep the better set of stats. This card converts that stacking event into a doubled snowball. Each time a creature you control mutates, the mutating pile gets a +1/+1 counter and you gain two life, so a body that is already growing in raw size also becomes a life-total engine, and the reward scales with how many times you re-mutate rather than how many creatures you play. That is the deliberate bit of the design: mutate naturally wants to keep piling onto a single body, and this rewards exactly that impulse instead of asking you to spread out. Note where the counter lands, though: it goes on the creature that mutated, not on the Symbiote sitting aside as an enabler. This card grows only when the mutate stack lands on it directly; otherwise it is a two-mana observer whose job is to be on the board first, watching, so every later mutate pays out. As a payoff wired to a narrow, short-lived mechanic, it lives and dies with that mechanic's density, but inside a deck committed to stacking creatures it turns a tempo plan into incremental life gain with no extra cards required.