Halfdane is a rare Legendary Creature — Shapeshifter card from Legends (LEG), collector number 229. Current market price: $35.97, TCGplayer market prices via Scryfall.
At the beginning of your upkeep, Halfdane's base power and toughness become equal to the power and toughness of target creature other than Halfdane until the end of your next upkeep.