Calamity, Galloping Inferno is a rare Legendary Creature — Horse Mount card from Outlaws of Thunder Junction Promos (POTJ), collector number 116p. Current market price: $0.48 (foil $0.55), TCGplayer market prices via Scryfall.
Haste Whenever Calamity attacks while saddled, choose a nonlegendary creature that saddled it this turn and create a tapped and attacking token that's a copy of it. Sacrifice that token at the beginning of the next end step. Repeat this process once. Saddle 1