Altered Ego is a rare Creature — Shapeshifter card from Shadows over Innistrad (SOI), collector number 241. Current market price: $0.25 (foil $0.70), TCGplayer market prices via Scryfall.
This spell can't be countered. You may have this creature enter as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.