Knight of the Mists is a common Creature — Human Knight card from Visions (VIS), collector number 36. Current market price: $0.07, TCGplayer market prices via Scryfall.
Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.) When this creature enters, you may pay {U}. If you don't, destroy target Knight and it can't be regenerated.