Stormsplitter is a mythic Creature — Otter Wizard card from Bloomburrow (BLB), collector number 154. Current market price: $2.12 (foil $3.22), TCGplayer market prices via Scryfall.
Haste Whenever you cast an instant or sorcery spell, create a token that's a copy of this creature. Exile that token at the beginning of the next end step.