Kathari Remnant is a uncommon Creature — Bird Skeleton card from Alara Reborn (ARB), collector number 23. Current market price: $0.23 (foil $0.51), TCGplayer market prices via Scryfall.
Flying {B}: Regenerate this creature. Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)