Singer of Swift Rivers is a rare Creature — Merfolk Shaman card from The Lost Caverns of Ixalan Commander (LCC), collector number 66. Current market price: $0.70, TCGplayer market prices via Scryfall.
Flash When this creature enters, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.) You may cast Merfolk spells as though they had flash.