March of Swirling Mist is a rare Instant card from Kamigawa: Neon Dynasty Promos (PNEO), collector number 61p. Current market price: $6.19 (foil $7.06), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, you may exile any number of blue cards from your hand. This spell costs {2} less to cast for each card exiled this way. Up to X target creatures phase out. (While they're phased out, they're treated as though they don't exist. Each one phases in before its controller untaps during their next untap step.)