Calamity Bearer

Damage doublers usually sit on the attacker: pump the creature, then swing for twice. This one moves the multiplier off the body and onto the type, and the design consequence is total. It does not care whether a Giant is attacking, blocking, or firing off an ability; any damage from any Giant source you control lands at double, so a burn-style tap ability, a fight effect, or a fistful of Giants trading in combat all scale at once. Because it is itself a Giant, it doubles its own combat damage too, so the modest 3/4 body swings as a 6-power threat while the rest of the tribe rides the same coefficient. That "source" clause is the crucial word: it catches noncombat damage the way most doublers cannot, turning a Giant that pings or deals damage on a trigger into a payoff rather than an afterthought. And because these are replacement effects that stack multiplicatively, two copies quadruple a Giant's damage and a third takes it to eight times; the coefficients compound rather than merely add. The whole thing rides on how narrow the tribe is: Giants are a scattered, high-cost creature type, so building a critical mass to abuse this is real work, and that scarcity is what keeps a permanent, no-strings damage doubler from tipping into oppressive. This is a tribal lord that pays off in reach and burst rather than stats, and the rare one that rewards a Giant deck for dealing damage outside of combat at all.