Yellowjacket, Heartless Marauder

The Villain payoff piece, and the trigger structure tells you exactly what kind of deck it wants. A 1/2 flyer for two mana that gains +1/+0 and lifelink each time another Villain enters is not built for the slow grind; because the boost stacks but wipes clean at end of turn, the reward is front-loaded into a single explosive turn. Land three Villains in one sequence and a harmless flyer becomes a 4/2 evasive lifelinker that can swing the race in one attack, then reverts to a 1/2 the moment the turn ends. That reset is the constraint doing the work: the card cannot sit back and accumulate value across turns, so it forces you to spend your Villains in a burst rather than dribble them out. The lifelink until end of turn is what keeps this from being a pure beater; a pump-only creature races and hopes to win first, while pump-plus-lifelink converts the same aggressive board into a life cushion, stabilizing and pressuring in the same swing. Flying narrows the field of things that can stop the accumulated power (it beats grounded blockers, though flyers and reach creatures still trade with it), which matters most on the turn you are cashing in a stack of triggers. What it lives or dies by is Villain density: pack enough of the shared type and this turns critical mass into reach and resilience at once, but leave the board thin and it never wakes up.