Sentinel of the Pearl Trident is a uncommon Creature — Merfolk Soldier card from Double Masters (2XM), collector number 67. Current market price: $0.22 (foil $0.28), TCGplayer market prices via Scryfall.
Flash When this creature enters, you may exile target historic permanent you control. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step. (Artifacts, legendaries, and Sagas are historic.)