Can't start quest for Succubus Classic

If you're level 20 but not seeing the quest offered by Gan'rul Bloodeye in Orgrimmar, it's possible you've already started the Undercity version of the questline.

Both orc and undead characters can begin this quest chain from either Undercity or Orgrimmar, but the starting location determines which version of the quest you follow. If you've accepted the quest from Undercity, the Orgrimmar version will no longer be available.

For detailed information on each version of the questline and find helpful guides, please refer to the Guide here.