This quest is not available in game.
Travel to Ratchet in the Barrens and speak with Wrenix the Wretched.
Zando'zan has seen it! Yes, the day comes! Thrall's death... the dagger in his back, poison seeping through to his every vein... Zando'zan has said too much.
<name>! Zando'zan has a task for <name>! <name> must travel to Ratchet, east of the Crossroads, and speak with Wrenix the Wretched. Go!