This quest is not available in game.
Using Dogran's Pendant, summon and subdue a succubus, then return Dogran's Pendant to Gan'rul Bloodeye in Orgrimmar.
Take this to the summoning circle in Neeru's tent, <name>. Summon forth a foul succubus, then show it your mastery. I believe in the strength of your magic. As always, though, be wary, for pride and overconfidence has overcome many a promising warlock.
When you have defeated it, return the pendant to me so that I might deliver the news to Zankaja.