Underground Facility Fractal

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Underground Facility Fractal

Underground Facility Fractal map.jpg
Map of Underground Facility Fractal

Fractals of the Mists

Fractals of the Mists loading screen.jpg
Loading screen


Underground Facility Fractal.jpg

Click to enlarge.

Delve deep into an underground dredge facility.

— In-game description

The Underground Facility Fractal is one of the Fractals of the Mists that occurs at levels 8, 29, 53 and 81.


  • Event boss (tango icon).png Find a way to higher ground.
    • Fractal Difficulty Scale: x
    • Personal Fractal Level: x
  • Event boss (tango icon).png Push deeper into the dredge stronghold.
    • Fractal Difficulty Scale: x
    • Personal Fractal Level: x
      (if bombs)
    • Use bombs to destroy the door.
      (if guns)
    • Assemble a firing team, arm yourself with dredge mining lasers, and destroy the reinforced door.
    • Reinforced Door
      Event bar.jpg Event swords (tango icon).png
    • Firing-team members present at door: X/3 (if guns)
    • Subdue dredge forces.
    • Dredge
      Event bar.jpg
    • Rabsovich
      Event bar.jpg Event boss (tango icon).png
      (if ice elemental)
    • Vanquish the rampaging ice elemental.
    • Rampaging Ice Elemental
      Event bar.jpg Event boss (tango icon).png
      (if power suit)
    • Destroy the dredge powersuit.
    • Dredge Powersuit
      Event bar.jpg Event boss (tango icon).png


Primary article: Fractals of the Mists#Rewards



Excluding Champion Rabsovich, Blind does work against the dredge in this fractal, unlike dredge in other areas of the game. Also, long lasting Protection and Regeneration can be stolen from some dredge.

First Room[edit]

There is a plate at the end of the left side path leading up from the first raised platform as you walk in. Have one person run up and stand on it to open the first gate. The player doing this only needs to stand on the switch long enough for at least one person to pass the gate, after which s/he can run back to rejoin the others. The plates do not remain depressed if the people on them are fully dead. The plates will remain depressed, however, if the players on them are only downed.

Next, one person stands on the plate on the upper right path that is just past the first gate. Again, the player only needs to stand on the switch long enough to let at least two other players through the second gate.

Once inside the central room, dredge will continuously spawn, so it's important to perform the rest of the procedure quickly. There are two plates in this room, one left and one right. Once both plates are activated, the door to the control panel will open. At this point, the person on the right side plate from earlier may come down and enter the middle room as well. While the control panel is accessible, it must be activated and allowed to run for about 20 seconds without interruption for the door to open to the next area. Long lasting stealth, such as from Shadow Refuge or Ash Legion Spy Kit, is useful for activating the control panel.

Dredge will spawn and try to attack the person using the control panel and the people on the plates. If either of the plates aren't being stood on, the control panel door will shut, interrupting the procedure. A common strategy for this is to allow the 4 party members who are not standing on the second button to get inside the room and, once inside, clear dredge around the room while ignoring the veterans. Then, have the two tankiest players stand on the buttons on either side of the room, at this point the 5th party member can run into the chamber and begin channeling the control panel while the remaining two party members kite dredge away from the control panel and side buttons.

Second Room[edit]

Next the players proceed either left or right to enter the next room. Which of the two rooms is open changes automatically on a daily basis.

Left room ("Rifles")

Once players kill the dredge leading into this area they will quickly note the orange AOE circles that appear in waves along the large ramp leading up to the right. These AOE circles must be avoided as they cannot be disabled. As players enter this area, on the left wall, will be a small box that players need to interact with to retrieve special Dredge Mining-Laser rifles. Upon picking up this bundle, players will lose all of their endurance and so be unable to dodge.

Players carrying rifles need to advance up this large ramp being bombarded with orange AOE circles. If hit while carrying a rifle, the rifle's 1 skill changes icon and using it will cause an explosion. If this happens, the player needs to move back down and retrieve a new rifle. The easiest way to move up the large ramp is to hug the left or right walls, when the ramp levels out, there will be a pocket of safe area along the left wall. Players need only to wait for the waves of AOE to move past them and then move out of this safe spot, continuing to the left and towards a large targetable gate.

Players will activate the 1 skill on the rifle to begin destroying the gate. After damaging the gate for about 9%, the rifle's 1 skill will become overheated, as if they were hit by the orange AOE circles. At this point, dredge will spawn near the gate that the party will need to kill. Then repeat this process, returning back down to the box to retrieve new rifles. After the gate is destroyed, the party progresses through to the next room and the next phase of this fractal.


  • Note that upon picking up the mining laser, your Endurance and Endurance Regeneration reduce to 0, removing the ability to dodge as long as the laser is held. Attempting to work around that restriction through endurance generation skills will cause your gun to overheat or explode upon dodging. Teleports and blinks will also cause the rifle to overheat or drop. This also applies to Daredevils, as while they are reduced to 50 Endurance rather than 0, attempting to dodge results in the laser being dropped.
  • Having swiftness is helpful here.
  • You can jump up the blocks on the left and right sides using the small pixel wide ledges. This can be tricky unless you know the right spot, so for the first time, try finding it after the AoEs have stopped firing.
Right room ("Bombs")

Clear the dredge leading up to this area by grouping them up using line of sight behind the pipe on the left wall. As you enter this area there will be a security dredge suit with a permanent aura denoted by a red circle around it. On the right side of the platform that this dredge suit is patrolling will be a partially caged section with a pipe that periodically dispenses 3 bombs. When these bombs are dispensed, dredge will appear to steal the bombs, they do not need to be fought, players merely need to quickly pick up the bombs to avoid the dredge stealing them. Once a player picks up a bomb, they will leave the caged area and to the right, against the back wall of the platform is a cloud of smoke constantly being released from one of the pipes. Players need to run through this smoke cloud to gain a long stealth. Players who move into the dredge suit's red aura will be revealed.

Once stealthed, players move up the hallway in front of them. Stationary turrets are located on either side of the hallway which create permanent security zones. These zones are demarcated by two straight horizontal red lines on the ground. Players who are unstealthed and run through these security zones will take damage, be stunned, and lose their bombs. Once a player makes it up to the end up of the hallway, there will be a pipe on the left wall to interact with and dispense bombs. 9 bombs in total are needed and the total number of bombs successfully deposited by your party will be shown in the top right of the screen. There is a second stealth cloud located opposite the bomb depository pipe that players will use to stealth back to the bottom of the hallway to retrieve more bombs and repeat this process.

When a bomb is deposited, several dredge will spawn near the bomb depository, they don't have to be dealt with, however, as long as players remain in stealth. As more bombs are placed in the depository pipe, more dredge security suits will spawn throughout the hallway, including one that will patrol on to the second stealth cloud at the top of the hallway. Players need to be careful of this dredge suit in particular because being revealed will cause the dredge at that end of the hallway to begin attacking any unstealthed players. The bombs have a 20s timer that begins upon pickup. It is displayed on the character's boon bar by the Bomb.png Bomb Timer effect. The stealth lasts quite awhile, but the player should be aware of how much time remains, as the bomb exploding will Reveal them.

Once 9 bombs are placed in the depository pipe, players will be able to interact with a detonator across from the pipe which will destroy the gate blocking the end of the hallway. It is advised for parties to group up at the detonator before destroying the gate since the dredge that have appeared during bomb placements do not despawn at this point. Progress through the destroyed gate to move to the next part of this fractal.


  • Make sure to hit both stealth stacking pipes.
  • Having perma swiftness makes this a lot easier.
  • If you know you won't have time to carry the bomb because of how the dredge have moved, head back and drop it.
  • You can jump on terrain to avoid some dredge, such as the stair's hand-railing.

Third Room[edit]

A champion dredge, Rabsovich, and a veteran dredge await you in this room for a mini-boss fight. This fight is fairly straightforward. He will be accompanied by a veteran dredge along with any dredge who your party pulled into this room from the previous phase, these can all easily be AOE'ed down with Rabsovich.

Rabsovich will periodically create an orange AoE rectangle leading out from his body in front of him. After a short delay, players in this AOE will take damage. He will also raise his shield throughout the fight and begin blocking all attacks while also dazing anyone who attacks him. During this time is a good chance for your party to take care of any mobs still alive around Rabsovich. He will continue to periodically spawn extra dredge from the dredge carrier, but these are easily cleaved out, as they spawn almost on top of him.

When Rabsovich dies, the dredge carrier will activate and drive through one of the walls. Continue through this broken wall to reach the next and final area.

Final boss[edit]

Final boss is either the Legendary Dredge Powersuit or the Legendary Rampaging Ice Elemental, with daily rotation.

Legendary Dredge Powersuit[edit]

The room is surrounded by a platform all the way around with buckets of molten ore and control panels for each on the platforms. The important mechanic for this boss fight is to use those controls to dump the buckets of molten ore onto the boss. Characters with shadowstep abilities may teleport up to the switch platforms, saving time and maintaining DPS. To do so, don't stand directly under the platform, but a little to one side, targeting the platform edge with the appropriate skill. Examples of shadowsteps include Thief's Infiltrator's Arrow, Mesmer's Blink, Elementalist's Lightning Flash, Necromancer's Necrotic Traversal, etc.

This boss has four basic attacks: an AOE stomp that does moderate damage, a standard physical 1-2 punch attack that does high damage, a large AOE attack where he pounds the ground sending up large dust clouds and doing moderate agony damage, and an AOE cluster bomb attack that does massive damage and can overlap, resulting in one-hit kills for even the most heavily armored characters. The bombs can be evaded while exploding by dodge rolling, though it's better just to move out of the blast radius.

The Dredge Powersuit also has a healing ability similar to a golem, where it plants itself in the ground, and the group must Interrupt the heal. If the boss is affected by the Champion of the Legions.png Superheated debuff from the buckets, this heal is interrupted by any damage done to the boss. If the boss is unaffected by the Superheated debuff then actual control effects need to be used. Condition damage is found to not affect him in the way it does normal mobs. At this point it is unknown whether this is intentional or a bug. [verification requested]

General Strategy

A significant feature of this boss is its health pool. The Legendary Dredge Powersuit has a massive health pool that makes it effectively invulnerable. This is where the buckets of ore come into play.

The general strategy is to have one player, preferably the character that is the most mobile, to climb up to the platforms surrounding the room to operate the controls for the molten ore buckets. The boss will become Fixated.png Fixated upon a particular player. If it is the bucket pourer, make sure someone is ready to switch places. The fixated player should kite the boss underneath a bucket (denoted by dark scorch marks), where the player at the controls can dump the molten ore on it, giving it the Champion of the Legions.png Superheated debuff. The debuff lasts 30 seconds and significantly increases the damage the boss takes, allowing it to actually be damaged effectively. From here, you can follow one of two strategies.

1. Break his defiance bar while dropping the lava, and do as much melee damage as you can, moving him once his debuff is at around ~5-10s remaining. The bucket pourer may generally drop down and help damage him. This method is extremely fast, and carries the risk of getting hit by melee attacks once the stun wears off.

2. (for groups with low melee damage or those with low crowd control skills) Continue kiting him from bucket to bucket, dealing consistent ranged damage. This method is much slower, but extremely safe, as it always ensures you have plenty of room to dodge his attacks and avoids his heavy hitting melee attacks. Not being able to stun him runs the risk of missing a bucket, however.

Using either method, take care not to take too long between lava pulls, as the self-heal easily heals 25%. Be sure to have all members kiting the mob stacked together and pulling in the same direction so if the Powersuit switches fixations on one character, he is still being pulled in the correct direction. This can create problems with evasion but is essential to quickly downing the boss. It is important to assign a secondary bucket activator in the case that the primary person goes down or becomes fixated.

When choosing a kiting path, the team can either go back and forth between two buckets, or kite around the room in a circular pattern. The back-and-forth path is easier on the person running the controls, as the distance is shorter, however the circular pattern is safer if a member of the team goes down, as they have longer to be revived.


  • When fighting the Powersuit reflection skills can protect from the bombs and bounce them back at the boss, however the reflected bombs deal no damage to the Powersuit.
  • Thieves, mesmers, and elementalists can shadowstep/blink/lightning flash up to most of the bucket platforms from the ground, enabling faster pulls and movement.
  • Bringing Crowd Control skills is recommended, as the additional debuff applied once his defiance bar is broken, in addition to his stun makes this a far safer and faster fight. It can also help the group position him if he is broken directly under the lava bucket. Be careful not to break him between buckets, as the extra time taken may allow him to get his heal off.

Legendary Rampaging Ice Elemental[edit]

This fight uses the same molten ore bucket mechanic as the Legendary Dredge Powersuit, and the effects of its attacks are similar. There are, however, two major differences.

First, while the Dredge Powersuit's cluster bomb attack fires in a fixed pattern around it, the Ice Elemental's Ice Shards directly target the players attacking it. Second, in addition to the Legendary Rampaging Ice Elemental itself, a number of Veteran Ice Elementals spawn and respawn during the fight, adding more danger to the fight. While these Veteran Ice Elementals will respawn infinitely, their spawn rate is slow enough that it can still be helpful to kill them, to reduce the number of threats on the field and make it easier to concentrate on the Legendary Elemental itself. They are also affected by the lava and take extra damage while overheated.

The Ice Elemental will occasionally visibly kneel and start healing the damage he has taken. The group should interrupt the heal by using a stun or knockdown skill on him, even if he is otherwise immune to the interrupting effect. This should be a priority for the group, since any healed damage will need to be re-inflicted, prolonging the fight. As with the Powersuit boss, Ice Elemental's self-healing will be interrupted by simply damaging them if they are affected by the Superheated debuff at the time.


Underground Facility Fractal Stabilizer Fractals of the Mists 5Achievement points
You've completed the Underground Facility fractal inside the Fractals of the Mists.Rabsovich's worst nightmare. 1 Fractal 5Achievement points
Master of the Molten Ore Fractals of the Mists 5Achievement points
Only use four buckets during the boss encounter of the Underground Facility fractal. Defeated the Boss of the Underground Facility Fractal While Only Using Four Buckets 5Achievement points
Stealth Bombers Fractals of the Mists 5Achievement points
Use stealth to bomb the reinforced door without triggering any security turrets or contractors within the Underground Facility fractal. Destroyed the Reinforced Door Without Alerting the Locals 5Achievement points
Carrier Cacophony Fractals of the Mists Central Tyria mastery point 5Achievement points
You made it through Rabsovich's onslaught without dying while inside the Fractals of the Mists.Not part of Rabsovich's plan. 1 Challenge 5Achievement points
The "Stealth Bombers" achievement might not be credited properly despite not triggering any turrets or contractors.






Entering the fractal
Dessa: Can you (static burst) Hello? The signal (static burst) interferences (static burst) higher ground. But (static burst) are everywhere (static burst) hear me? Higher. Ground.
Fighting the dredge champion
Champion Rabsovich: To battle!
Fighting the Legendary Dredge Power Suit
Legendary Dredge Power Suit: Now you die!
Legendary Dredge Power Suit: Fear the collective!
After defeating the final boss
Dessa: There! Finally, a solid signal. Everything looks stable, too. You can depart when you're ready. So, did I miss anything?

Related achievements[edit]

Upon completion[edit]

Objective during[edit]


  • Which path you had to take (bombs or guns) used to depend on the fractal level, but after the rework the paths are randomly selected every time the instance is opened.
  • Until the 26th June 2018 update, three party members needed to use rifles at the same time to damage the door.