Subversive Acolyte

A 2/3 for two mana is a reasonable early blocker, but the once-only fork carries the whole point: you commit permanently to one of two creatures, and the choice tells your opponent which game you have decided to play. The Human Cleric branch turns it into a durable 3/4 lifelinker that stabilizes a race and shrugs off smaller removal; the Phyrexian branch inflates it to a 5/5 trampler that punches through blockers but drags a leash behind it, converting any combat or burn damage it takes into a proportional sacrifice of your own permanents. That clause is what disciplines the aggressive line: a chump block dealing two damage costs you two of your own permanents, so the Phyrexian body wants to swing unblocked or trade cleanly rather than absorb hits. What makes the card sharp is that it pins both halves of black's identity to a single shell. One branch is the grinding lifegain-and-attrition plan; the other is fast, self-immolating Phyrexian aggression that treats your own board as fuel. You spend mana and life to transform, the flip is irreversible, and once-only means there is no hedging: the card rewards knowing which fight you are in before you commit rather than keeping the option open. Two creatures live inside one two-drop, and the design forces you to pick which one you needed.