You must also return the Soul Cannon.
You will need:
- Subdue Reth'hedron the Subduer
- Soul Cannon (Provided)
Grouped players can complete this quest if they remove at least some of Reth'hedron's HP, alive or not as long as they are close to the portal when Reth'hedron passes through it.
- Max Level Method
Due to the nature of scaling and gear, a player at max level will kill Reth'hedron with the quest item before the objective can be completed. In order to satsify the necessary objectives, take off all of your gear and acquire the ressurrection sickness debuff. This will reduce your damage scaling enough so the Soul Cannon doesn't kill Reth'hedron.
- Method 1
A relatively easy way to accomplish this quest is to stay mounted and strafe around Reth'hedron in circles while channeling the Soul Cannon to avoid the fireballs. Getting dismounted will in many cases get players killed. Be certain to maintain distance from Reth'hedron laterally, as Reth'hedron will melee lightly-armored players for ~3000 and disrupt the channel. Remember that mobs ignore the z-axis, so if players are immediately above Reth'hedron, he will swing his fists.
Once Reth'hedron's HP has reached 10%, he will path towards the Twilight Portal. Keep channeling the Soul Cannon as he walks away, but stay out of melee range.
- Method 2
There is a second and even easier way to accomplish this quest. Fly around the top of the portal and activate the Soul Cannon when Reth'hedron is close to the portal. Then fly to the top of the portal and land on the back of it. You have to make sure you aren't too far away from Reth'hedron or he will continue on his normal path. When you stand here, the fireballs and shadowbolts can't hit you. Occasionally he will try to cast Cripple, but you won't receive this debuff.
When Reth'hedron reaches 10% he will start to walk away towards the Portal. Now you just have to follow him until he is totally drained. During these last seconds he won't attack you, so just fly behind him. At 1% he will go through the portal and you will have completed the quest.
<Balthas holds up an alien looking device.>
This is a soul cannon. Its effects are devastating when attuned. This one is attuned to my blood. The same blood flowing through the veins of Reth'hedron - my brother. Aye, his misplaced allegiance will be the end of him.
Take the cannon and fly to the Twilight Ridge in western Nagrand. Locate Reth'hedron and fire! You must stay on your mount and within range for the effects to take hold. Stand your ground against him and he will have no choice but to flee!
Is it done?
He will be back, but for now the Legion's war against Lord Illidan is weakened. He shall know of your deeds, captain.