Call of the Nightwing is a uncommon Sorcery card from GRN Guild Kit (GK1), collector number 8. Current market price: $0.31, TCGplayer market prices via Scryfall.
Create a 1/1 blue and black Horror creature token with flying. Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)