Rhox Faithmender

A 1/5 body that taxes nothing and threatens nothing is the right vessel for an effect this dangerous: the doubler stays on the table because the rhino itself cannot pressure you back. The clause is the engine. Every life-gain source in the deck reads twice as large while this sits in play, and the math compounds: stack two copies and one point of lifelink becomes four. That kind of multiplier needs a body that survives, not one that races, which is why white's lifegain shells and Soul Sisters builds reach for a wall rather than a beater. The defensive stat line is also what keeps the card honest. A doubler attached to a real threat would warp games on its own; pinned to five toughness, it does only what you build it to do. It is not inert on its own, either: its own lifelink feeds the doubler, so even an unsupported swing returns two life, the floor of an effect that wants to climb. It belongs to the small family of permanents that change a number rather than a board, the lifegain analog to mana doublers and damage doublers, and it shares their weakness: drawn without the engine around it, the trickle barely registers. The reward is for the deck that already gains incidentally and wants the slope to steepen. Everything turns on the gap between the trivial body and the exponential text, and that gap is the whole point.