Dominating Vampire

Threaten effects have always paid for their power with impermanence: you borrow a body for one attack, sacrifice or bounce it before the turn ends, and hand it back if you cannot. What this Vampire does is fold that entire play pattern into a tribal payoff. The size of the theft scales with your board, so a developed Vampire deck steals bigger and bigger targets while a mono-red brew running one or two barely functions. That is the balancing lever: the effect is worthless as a splash and lethal as a keystone, and the deck has to earn its ceiling by committing to the type in the first place. Untap and haste are the operative words in the timing: even a defensive blocker becomes an immediate attacker, which turns the steal into tempo and reach at once, not merely a removal-adjacent tap-down. And because the theft is stapled to a 3/3 that stays on the board after the borrowed creature goes home, the card does not cannibalize its own tempo the way a one-shot spell does; it stays behind and adds to the very Vampire count that fuels the next payoff you deploy. Plenty of red creatures convert an enters-the-battlefield trigger into an aggressive swing, but the mana-value clamp keyed to your own tribe is the wrinkle that makes this a build-around rather than a generically good beater.