Djinn of Infinite Deceits

The 2/7 body is the whole ergonomics of this thing: a wall that survives long enough to keep tapping, holds the ground while it reshuffles ownership of the board, and never wants to attack anyway. What it taps for is the rare two-way Donate effect built into an activated ability rather than a one-shot spell. Most control-stealing in blue is theft (take their best thing, keep yours); this instead swaps two creatures, which means the natural play is to trade your worst creature for their best one, or to weaponize a downside creature by handing it across the table. The nonlegendary restriction keeps it from rifling through legendary creatures. The combat exclusion is the real leash, but it leashes only one phase: you can still untap and exchange at instant speed on an opponent's end step or in response to a spell, just not mid-attack to ambush a blocker or yank an attacker out of a swing. That single carve-out is doing precise work; it walls off the most degenerate tempo line (stealing into a lethal combat) while leaving the rest of the turn open for ambush exchanges set up around someone else's resources. The repeatability is the payoff for the slow clock and the double-blue cost: left unanswered, it turns a stalled board into an open negotiation where you always get to take the better half.