Xenagos, God of Revels

Doubling power is the cheapest way to make combat math fall apart, and this is the engine that does it without asking for a build-around. The combat trigger fires automatically, every turn, on another creature you already control: it grants haste and adds that creature's own power to itself, so a 4/4 swings as an 8/8, a 7/7 as a 14/14, and anything with trample or double strike crosses from threatening to lethal in a single step. The devotion clause is what pays for that ceiling. Until your red-and-green pip count hits seven, the body sits on the battlefield as an indestructible enchantment that still triggers, doing all the work while presenting nothing to attack into. Once the threshold is met it becomes a 6/5 attacker in its own right, but the trigger never touches it: the buff always lands on someone else, so the god is the catapult, not the projectile. That split (always-on enabler, conditional attacker) is the design tension of the Theros god frame, and this is the version built for the turn the game ends rather than for grinding incremental value. It does not generate cards or untap lands; it picks the largest other thing you have and points it at a face. The lineage it sits in is the Gruul "one big swing" tradition, and few cards in that color pair convert a midsized creature into a kill as bluntly or as repeatably.