Haakon, Stromgald Scourge is a rare Legendary Creature — Zombie Knight card from Coldsnap (CSP), collector number 61. Current market price: $2.54 (foil $28.13), TCGplayer market prices via Scryfall.
You may cast this card from your graveyard, but not from anywhere else. As long as Haakon is on the battlefield, you may cast Knight spells from your graveyard. When Haakon dies, you lose 2 life.