Resplendent Mentor

What this turns each of your white creatures into is a Soulmender you have to tap, and that conversion is the whole gambit. The body is a 2/2 for five, which prices the card entirely on its anthem-of-lifegain effect rather than on combat. Spread across a wide white board, the math compounds: ten creatures means ten potential life per turn, but each point costs you a tapped attacker or blocker, so the engine and your battlefield presence fight over the same resource. That tension is the design's honesty; the lifegain is real but never free, and you cannot both swing wide and drink deeply in the same turn. It also rewards going wide on quantity rather than depending on a single payoff, since the value scales with how many white bodies you can keep alive rather than with any one of them. The effect quietly grafts an activated ability onto creatures that did not have one, which matters anywhere a tapped-creature trigger or a "creatures with activated abilities" subtheme wants more bodies to count. On its own it generates incremental life and nothing more; the question it poses to a deck is whether a slow, repeatable life faucet is worth a five-drop that contributes almost nothing to the board the turn it lands.