Heart of Kiran is a mythic Legendary Artifact — Vehicle card from Aether Revolt (AER), collector number 153. Current market price: $0.39 (foil $0.72), TCGplayer market prices via Scryfall.
Flying, vigilance Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.) You may remove a loyalty counter from a planeswalker you control rather than pay Heart of Kiran's crew cost.