You must have either killed or quested stuff to lower your faction or else you chose a diety for your dark elf enchanter. Dark elves using illusions are able to do this quest unless they tanked faction or are not agnostic.
I'm not sure what faction is required for the quest, Inhabitants of Firiona Vie probably. You can try to raise that by killing goblins on Kunark in Warsliks Woods and Lake of Ill Omen but if you have a religion it would take TONS of faction work and illusion and faction spell to even have a chance.
Ideally and quickest is to now have another character do the quest for you. Anyone can do this quest, not just enchanters. The spell scroll you get is tradeable so go ahead and get another character of yours or a friend to do this quest and then you can buy or take it from them.