Veiled Serpent is a common Enchantment card from Dominaria Remastered (DMR), collector number 72. Current market price: $0.14 (foil $0.06), TCGplayer market prices via Scryfall.
When an opponent casts a spell, if this permanent is an enchantment, it becomes a 4/4 Serpent creature with "This creature can't attack unless defending player controls an Island." Cycling {2} ({2}, Discard this card: Draw a card.)