Duskmantle Guildmage is a uncommon Creature — Human Wizard card from Gatecrash (GTC), collector number 158. Current market price: $0.65 (foil $10.06), TCGplayer market prices via Scryfall.
{1}{U}{B}: Whenever a card is put into an opponent's graveyard from anywhere this turn, that player loses 1 life. {2}{U}{B}: Target player mills two cards.