Fall of the Impostor is a uncommon Enchantment — Saga card from Kaldheim (KHM), collector number 208. Current market price: $0.28 (foil $0.28), TCGplayer market prices via Scryfall.
(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.) I, II — Put a +1/+1 counter on up to one target creature. III — Exile a creature with the greatest power among creatures target opponent controls.