Dread Fortress operations Patch 2.4 SWTOR

SWTOR Corruptor Zero Dread Fortress operation guide

A guide to defeating Corruptor Zero, the fourth boss in Dread Fortress, one of the two new operations introduced with Patch 2.4.


Loot: Unassembled Arkanian Offhand, 1 random Underworld Token, 1 random piece of Verpine gear (no set bonus) 1x Exotic Element Equalizer, 4 Elite Commendations.

HP: 1.4 million (8m)

Recommended gear: Artifact gear or above. You may want to have some Black Market/Arkanian gear just to be safe.

Differences from hardmode

Identical mechanics to hardmode except there is no tank swap, no Concussion Mine and the Unified Beam doesn’t really one shot you unless you are low in HP.


October 15 changes

  • Concussion Mine now has a cast bar but it is very buggy. You get two versions of Concussion Mine, a fake non-stacking Concussion Mine and a real stacking Concussion Mine debuff. You just need to deal with the stacking version as the fake one deals no damage but the debuff icon remains on the player until they die/zone out.
  • In addition to the buggy icons, Concussion Mine is now doing significantly much more damage (more so than in the video)
      • 5.5 k damage at 1 stack
      • 8.5k damage at 2 stacks
      • 11.3k damage at 3 stacks.
      • 14k damage at 4 stacks.



HP: 2.26 million (8m)

Loot: Unassembled Dread Forged Offhand (rating 178), 2 random pieces of Oriconian gear (rating 178, no set bonus), 2x Exotic Element Equalizer, 6 Ultimate Commendations, 8 Elite Commendations, and Corruptor Blade (orange mainhand/offhand legacy weapon)


Recommended gear: Underworld/Verpine. Kell Dragon is more than sufficient.

Enrage timer: Unknown

Key Mechanics

Tank Swap

  • Tank receives a stacking debuff from boss that forces them to tank swap at 4-6 stacks.

Concussion Mine

  • Appears to be a casted at random raid member sometime during the fight (no exact % but has a cast bar). Whoever gets this stacking debuff will near AoE damage to themselves and rest of the raid. They will need to run to the boss and damage him with this ability to get it removed.


  • Droid adds that spawns before and during the fight. One of them will target a random raid member and put down a red circle with Missile Salvo.

Melee Mode

  • Massive Slam – a PBAOE that deals around 4k damage.
  • Heavy Slash – Channeled attack on tank that does a ton of damage. Healers/tanks need to be ready for this. Leaves a Bleed at the end (Physical) that can be cleansed by operatives/scoundrels and commandos/mercs.

Ranged Mode

  • Anti-Gravity Field – red circle casted on tank that lifts them and cause aggro drop if not avoided.
  • Chest Laser – Channeled attack w/ DoT that should be cleansed (tech)
  • Missile Barrage – raidwide AoE centered on each person, spread out to lessen damage.

Past 20% mode

  • Unified Beam – Laser attack past 20%, anyone caught in the path of the beam will be instant-killed. Adds at this point become melee.

Tank Swap

Tanks will be receiving a stacking debuff from the boss that increase the boss’s damage dealt to them so they will need to swap after 4-6 stacks. Swap at lower stacks if your tanks can’t handle the damage.


Concussion Mine

This is a new mechanic introduced to hardmode on live and it is something you have to beware as it can potentially wipe your raid if not handled properly. At a random time during the fight, one random raid member will get a debuff icon shaped like a mine. This debuff keeps stacking up and deals increasing AoE damage to the player and anyone around him. You will see him casting it but you can also tell if this debuff is is on your via your debuff icon or if you see a sphere keeps exploding over your character. When you receive this debuff, you will need to run next to the boss and damage him with this AoE attack to remove it.

  • As of the October 15 patch, he also throws out fake Concussion Mine icons that does stack and deals no damage. Ignore them.
  • Concussion Mine damage have being significantly increased as of the October 15 patch, he nows deals much more damage per stack.
    • 5.5 k damage at 1 stack
    • 8.5k damage at 2 stacks
    • 11.3k damage at 3 stacks.
    • 14k damage at 4 stacks.



Before you get to fight Corruptor Zero, you will need to face a large group of adds. The two adds to note are the D-03 Repair Droid which heals other adds and the D-15 Corruption Droid which drops a red circle on a random member and casts Missile Salvo on that player. Whoever receives that red circle needs to stay away from other players to prevent collateral damage. Missile Salvo hits for about 8k damage. Offtank will need to grab the adds and tank them.

  • D-15 Corruption Droid can be crowd controlled to lessen the damage.


Melee mode

When Corruptor Zero is in melee mode, he will use the Massive Slam and Heavy Slash abilities. All of the droid adds that he spawns will be ranged. 


Corruptor Zero himself have a PBAOE (Proximity based AoE) attack in melee mode called Massive Slam that deals around ~4k damage per slam. The cast time on it is only 0.5s but as long you stay a bit of distance away from him the attack isn’t something to worry about.


Healers and Tanks need to be aware of a channeled attack from Corruptor Zero called Heavy Slash. This is 3.5s channel that does a ton of damage to the targeted tank so be sure to pop defensive CDs if you see this attack coming up. It leaves a Bleed DoT (physical) that can be cleansed by operatives/scoundrels and commandos/mercs.


Ranged Mode

When Corruptor Zero is in ranged mode, he will used the Anti-Gravity Field, Chest Laser, and Missile Barrage attacks exclusively. All of the droid adds he spawn will be melee.


Anti-Gravity Field is a large red circle around Corruptor Zero that tanks and melee DPS need to get out of ASAP. This red circle not only lifts those who fail to get out (stun breakers does not appear to work here), it also cause aggro drop which can be a serious issue for tanks caught in the circle. Tank swap here if the main tank is caught inside the circle.


Chest Laser is the equivalent of Heavy Slash in melee mode, it is a channeled attack that applies a DoT at the end (tech) which should be cleansed. Normally this attack is reserved for tanks but if the tanks fail to get out of Anti-Gravity Field, Corruptor Zero will switch to the next highest threat and this attack can kill a DPS/healer easily.


Missile Barrage is the equivalent of Massive Slam in melee mode but this is a raidwide AoE centered on every raid member instead of a PBAOE. You will need to spread out to prevent overlapping damage (it is like the Titan 6 fight). This is not a channeled attack but rather there is a slight delay between the cast and the arrival of missiles so he can use other attacks while missiles are homing down your raid.


Unified Beam

Corruptor Zero goes into this mode shortly after hitting the 20-30% mark. He will randomly teleport to a section of the room (the room is shaped like a cross) and shoot his giant lasers. Anyone caught in the path of the laser will be instant-killed (even if you stand on the sides, the laser will still kill you). The trick to avoiding the laser is to 1) Mark Corruptor Zero so you know where he is and 2) Run to a corner and stand in the section of the cross that is diagonal to the beam (a simpler way to put this is don’t be in line of sight of the beam).

  • The beam hits for ~50k damage so if you have any denfensive cooldowns that can reduce the damage or block the damage you may able to survive it.

Where he lands for the first time is random but after that he switches to the opposite half the cross so as long you are standing in the section where he was standing with the previous beam you won’t die to the beam.  


By Dulfy

MMO guide writer and blogger. Currently playing and covering SWTOR, GW2, and TSW.

34 replies on “SWTOR Corruptor Zero Dread Fortress operation guide”

We noticed another mechanic in 8-man HM today. Sometime at 40% HP, a random player will receive a stackable debuff called Concussion Mine, that does AOE damage to all surrounding players. The player with this debuff has to run into the boss immediately. As soon as the boss is damaged by the debuff, the debuff will be removed. Alternatively, Scoundrels can remove the debuff by going into stealth. If you don’t do this, the damage dealt by the debuff will become unhealable sometime around 12 stacks, and when the player dies and receives a battle-rezz, he will lose the debuff as well.

Hi Dulfy, I got this mainhand legacy weapon from corrupter zero in dread fortress HM. Havn’t seen it anywhere else so might be first to post about it and though that this is the best place to post it. Tell me if you want more pics.

You can see the item tooltip in his picture, it reads “Requires Vibrosword”.

On a not-entirely-unrelated note: DO WANT! :S

PS. Maybe it’s just me, but I found that last sentence about the opposite half a bit confusing. I do get how the beam works, but I really don’t think ‘opposite’ is the word to use here: if I were on the western ‘branch’ of the cross, then the opposite half would be the eastern ‘branch’, not the line perpendicular to the one I’m on. I think the clearest explanation could be to say that if he’s in the east or west branch, go north or south (and vice versa).

PPS. Compulsory thank-you note for amazing guides! <3

I do not think Concussion Mine is Random its not % based either we got it 100% of the time during the 3rd set of adds.

We killed the guys yesterday, it took us around 10-15 wipes to achieve that and during those attempts we did received concussion mine only once. Not once per fight, but once per 15 tries. I don’t know if we were THAT lucky or is it THAT rare.



Yea tonight was different for us also in 2 raids the 1st was every 2nd wave of adds and the 2nd run was every wave of adds.

new info regarding Concussion Mine:

– it goes out more often then once per fight

– it can target anyone within your raid but can be dispelled within first tick

I just checked logs for our 4 attempts last night and it was applied three times in 2.5 minute fight.

a) Once went to healer that boss did force leap soon after to, so after second tick it dispelled

b) Second time went to melee – dispelled straight away as he was attacking boss at that time

c) Third time landed on our commando dps and was ticking whole raid for 9k of damage which caused us to wipe on that try

We didn’t know about this new debuff on Live servers so this wiped us and as we only had like 20 minutes for few tries on him, i wasn’t checking logs for damage received at that time.

So if your group is melee heavy, heave your healers close to boss and you got lucky with RNG it is possible not to see this debuff once during whole fight as its is applied and then dispelled within a second:

00:40:46.924 Corruptor Zero’s Concussion Mine adds effect Concussion Mine to Maarik.
00:40:47.053 Corruptor Zero’s Concussion Mine adds effect Concussion Mine to Maarik.
00:40:47.053 Corruptor Zero’s Concussion Mine effect of Concussion Mine fades from Maarik.
00:40:47.420 Corruptor Zero’s Concussion Mine hits Maarik for 713 kinetic damage, causing 713 threat.

another annoying thing is his red circle stun skill – we have tank and dps run away from it only to ne pulled back and stunned. You can see it here:

Really annoying and causing few wipes just from tank getting stunned then killed from it even though he swears he is outside of his red circle.

we are stuck on this boss atm but when i see things like this sometimes i think its not that fair of a fight 😉

with the concussion mine, we’ve had a couple of people have the mine debuff at the same time but not the damaging stacking one, does one of the adds activate that with an ability?

Mostly because this is the 3rd time they trying to fix it and it bugged it in the process. You will have some people die during the unified beam phase to the mine. Just ignore your losses, rez if you can and push on.

Are you sure the Bleed DoT left by Heavy Slash is Physical ? You add that’s it must be cleansed by a Op/Merc. As far as I know Tech is the only DoT type that sorcerer healers can’t cleanse, as they have a talent to cleanse Physical as well as Force and Mental

Has anyone else noticed if a side effect of the Anti-Gravity Field is that he attacks with one knockback anyone caught inside? Our maintank would keep aggro, not get caught, but he would still attack others that were caught.

Tip if you are having the same problem getting out of the red as I am- I’m an east coaster on a west coast server, so where I think I am and where the game thinks I am are often quite far apart- if you jump, that makes the server update your position. So if you jump as you exit the circle, that will help make sure you don’t get unjustly annihilated.

Yes, there is a timer for the anti-grav field. One of the ranged dps in my group keeps track of it though and just calls it out because I’m a lazy tank. The first one drops at 30 seconds though, or some multiple of half a minute. If he’s moved/moving during the anti grav field drop the timer gets thrown off.

There is a rotation to it.. 3-1-4-1-2-3 That order will depict when his gravity vortex comes out. So he’ll do 3 concussion mines then gravity vortex then 1 so on so forth.

Does the still drop the HK-51 customization or was it removed together with the watchtower customization? (By the way does anyone know why they removed it?)

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