Ghostly Flicker

Two permanents leave and return at instant speed, and the entire combo lineage of this card lives in that "and return" clause: every arrival ability queues up fresh, every tapped permanent untaps, and every effect keyed to a permanent's most recent entry resets. The blink reads first as a value tool: pull two creatures out of a targeted removal spell's reach in response, untap your lands for a fake-out mana boost, refire a pair of ETB engines on demand. But the design's real weight is offensive, because flickering exactly two permanents at once is the precise shape a two-card mana engine needs. Pair it with a creature that nets mana when it enters (Peregrine Drake and Palinchron are the classic partners) plus any way to repeat the flicker, and the loop produces infinite mana, infinite ETB triggers, or both. The instant-speed timing is what makes it dangerous rather than cute: the loop assembles on an opponent's end step, outside the reach of sorcery-speed answers, and returning the permanents "under your control" sidesteps the temporary-control problem that dogs older blink effects. Among the repeatable-blink instants that turned ETB value creatures from a midrange subtheme into a combo axis, its distinguishing feature is the doubled target count, which makes the spell a closed loop with the right partner rather than just a tempo trick.