Spark Double is a rare Creature — Illusion card from War of the Spark Promos (PWAR), collector number 68p. Current market price: $8.46 (foil $13.51), TCGplayer market prices via Scryfall.
You may have this creature enter as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.