Melancholy

A color-pie inversion built as a leash rather than a kill. The body is a Paralyze descendant: tap the creature on entry, then deny its untap step to keep it down. What changes the math is the recurring black pip the controller must pay every upkeep or the Aura falls off. That single mana sounds trivial, but it competes with everything else you want to do and scales painfully if you try to lock down more than one threat at once. The structural quirk worth noting is that this never removes the creature; it only neutralizes it, so the locked permanent still feeds devotion, still counts toward tribal totals, still triggers anything that cares about its presence on the battlefield. That makes it softer than destruction or exile, and it is genuinely soft: the Aura stays attached even if the creature finds a way to untap, so the lock reasserts itself the moment that creature taps again for any reason. The clean escape is to move the creature out from under the enchantment entirely (a blink effect strips the Aura along with everything else), not to untap once and walk free. Handing the permanent-tapping job to black, where blue historically owned this kind of soft-lock, is what the design exists to test: the color that usually answers a threat by killing it outright is asked instead to keep it pinned, with the tax priced in black mana to keep the lock from being free.