Nether Traitor is a rare Creature — Spirit card from Time Spiral (TSP), collector number 120. Current market price: $9.68 (foil $26.97), TCGplayer market prices via Scryfall.
Haste Shadow (This creature can block or be blocked by only creatures with shadow.) Whenever another creature is put into your graveyard from the battlefield, you may pay {B}. If you do, return this card from your graveyard to the battlefield.