Stonybrook Banneret is a common Creature — Merfolk Wizard card from The Lost Caverns of Ixalan Commander (LCC), collector number 173. Current market price: $0.66, TCGplayer market prices via Scryfall.
Islandwalk (This creature can't be blocked as long as defending player controls an Island.) Merfolk spells and Wizard spells you cast cost {1} less to cast.