Splinter Twin is a mythic Enchantment — Aura card from Special Guests (SPG), collector number 167. Current market price: $6.85 (foil $8.24), TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature has "{T}: Create a token that's a copy of this creature, except it has haste. Exile that token at the beginning of the next end step."