TheWoWDBi was having problems with the gun killing him in three hits at level 90, but I was able to complete the quest after all.
After removing my armor and weapons I was able to lower him below 10%hp and then trigger the gun to complete the quest.
Hope this helps in a post 6.0 world
Quest
Subdue the Subduer
A World of Warcraft quest in Shadowmoon Valley. Facts and objectives from the current retail game data.
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
Really easy one. Drain his health down while you are in the air with your flying mount. Avoid meteors/fireballs.
The tactic I used is basicly staying in range, above him, flying around him clockwise while draining his soul. This way you will only take the shadow bolt damage (800ish). If you get cripple on you start going anti clockwise, so you dont run into the fireballs. The fireballs really hurt also dismounts you, and you die. Will take you a while till you suck his soul out, once hes on 1% hes starting to walk to the portal and leaves the place.
If you seem to take too much damage during an attempt you can flee away by just flying far from him.
Fun quest, good luck on it!
For level 90s:
1. First thing you will want to know is it does pop up on screen when this quest is completed.
2. Take off all your gear and get resurrection sickness.
3. Cancel the channel of the Soul Cannon by pressing escape when Reth' Hedron is at 1% health (really small sliver of health).
4. Allow him to walk away into the portal
Quest facts
LevelLevel 25-30
Quest ID11090
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(11090))
Requirements
ReputationNetherwing: Honored or higher
Read from the Blizzard quest API.
Description
<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!
Community notes from Wowhead · 348 comments
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TypePlate Head
Item level32
BindingBinds when picked up
Armor19
Stats+7 Strength or Intellect, +11 Stamina, +9 Parry, +12 Dodge
Suited toHoly, Unholy, Protection, Retribution, Arms, Fury, Blood, Frost
Sells to vendors for36 gold30 silver
TypeLeather Chest
Item level32
BindingBinds when picked up
Armor11
Stats+7 Agility or Intellect, +11 Stamina
Suited toBalance, Restoration, Mistweaver, Devourer, Vengeance, Feral, Guardian, Brewmaster, Subtlety, Outlaw, Assassination, Havoc, Windwalker
Sells to vendors for48 gold15 silver
TypeWand Ranged
Item level32
BindingBinds when picked up
Weapon3 - 5 damage, speed 2.0
Stats+4 Intellect, +6 Stamina
Suited toFrost, Fire, Arcane, Destruction, Affliction, Discipline, Holy, Shadow, Demonology
Sells to vendors for86 gold92 silver
TypeMail Legs
Item level32
BindingBinds when picked up
Armor15
Stats+7 Agility or Intellect, +11 Stamina, +12 Critical Strike
Suited toElemental, Restoration, Devastation, Preservation, Augmentation, Marksmanship, Beast Mastery, Survival, Enhancement
Sells to vendors for48 gold33 silver
Reputation: Netherwing +500
This unusual brood of dragons was spawned from the eggs of Deathwing's black dragonflight, and infused with raw nether-energies. Now, they seek to find their identity beyond the shadows of their father's destructive heritage.
Reputation group: The Burning Crusade.
Other quests in Shadowmoon Valley that reward Netherwing reputation: Ally of the Netherwing (+42,000), In Service of the Illidari (+250), Netherwing Crystals (+250), Nethermine Flayer Hide (+250), Netherdust Pollen (+250), Nethercite Ore (+250).
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.