Enslave

Control Magic in black's clothing, and the color-pie translation is the whole exercise. Blue's permanent steal effects (Control Magic, Treachery, Mind Control) take the creature clean and keep it forever; black is not supposed to get something for nothing, so the theft comes with a bill attached. The enchanted creature deals 1 damage to its owner each of your upkeeps, which inverts the usual penalty: instead of paying for the steal yourself, you bleed the person you took it from. That is the structural twist that makes this a black card rather than a recolored blue one. Black steals by exploitation, not domination, and the upkeep ping is the exploitation made literal. The cost is the rest of the discipline. Six mana is a heavy tax compared to blue's three or four, and the trigger does nothing if the creature dies or gets bounced, which leaves you down a card and a card-and-a-half of mana with the opponent's body back in their hands. Permanent control still lands hardest on the biggest threat on the board, and the slow drain on top means the original owner cannot even enjoy having lost it. As a piece of color-pie engineering it is a tidy answer to a real question: what does black's version of Control Magic look like when the color is forbidden from clean acquisition?