Autarch Mammoth is a uncommon Creature — Elephant Mount card from Aetherdrift (DFT), collector number 153. Current market price: $0.18 (foil $0.25), TCGplayer market prices via Scryfall.
When this creature enters and whenever it attacks while saddled, create a 3/3 green Elephant creature token. Saddle 5 (Tap any number of other creatures you control with total power 5 or more: This Mount becomes saddled until end of turn. Saddle only as a sorcery.)