Spare Changeling is a common Artifact Creature — Shapeshifter Treasure card from Unknown Event (UNK), collector number CZ02. Current market price: $30.24, TCGplayer market prices via Scryfall.
Changeling {T}, Sacrifice this artifact: Add one mana of any color. Whenever you pay an additional cost while casting a spell, you may return this card from your graveyard to your hand.