Ostrich-Horse is a common Creature — Bird Horse card from Avatar: The Last Airbender (TLA), collector number 188. Current market price: $0.12 (foil $0.23), TCGplayer market prices via Scryfall.
When this creature enters, mill three cards. You may put a land card from among them into your hand. If you don't, put a +1/+1 counter on this creature. (To mill three cards, put the top three cards of your library into your graveyard.)