The Soul Cannon of Reth'hedrons is a collection quest, having players collect several trade goods and a quest item from Sar'this in Lake Jorune above Stonebreaker Hold in Terokkar Forest. This quest is available at honored reputation with Netherwing.
You will need:
Raw Materials Breakdown:
Reth'hedron now lords over the Twilight Ridge of Nagrand. An eredar of such power being loosed upon this world does not bode well for the Illidari. Alas, we do not have the resources required to slay Reth'hedron. Not with the war the bastards have brought to the Black Temple. No... I have a better plan.
You will subdue Reth'hedron, banishing him back through the Twilight Portal. For this a soul cannon must be fashioned.
Return to me with the materials on this list.
Have you gathered the components required to fashion the soul cannon?
<Balthas deftly combines the components you brought him.>
You are now ready for the second phase of the plan, captain.