Daru Mender

Regeneration with a built-in feint. The morph mechanic exists to let cheap, situational effects masquerade as a generic 2/2 until the moment they matter, and a regeneration trigger is one of the better fits for that disguise: nobody plays a one-mana regeneration enabler on the off chance combat goes sideways, but everybody plays a 2/2 they can flip for one white to undo a removal spell or save a blocker mid-combat. The unmorph cost is white and a single mana, so the flip can happen at instant speed in response to a combat trick or a kill spell, which turns a passive board piece into a reactive answer without telegraphing it a turn early. What constrains all this is that the regeneration is a one-shot tied to the flip, not a repeatable shield, so the timing has to be exact: you spend your face-down ambiguity for a single save, and once it is face up it is just a 1/1 Cleric. As a creature in the soldier-and-cleric tribal era it was built for low-rarity board presence with a sliver of utility stapled on, the kind of common that rewards a player who reads the stack rather than one who reads the body. The effect is narrow enough that it never defined anything, but it is a clean miniature of why morph was such a useful tool for designers: any effect, however marginal, can be sold as a 2/2 first.