Source: Dulfy (and thanks to all the Oops'lings who helped create the class-guides and changes to the boss-guide).
SABETHA THE SABOTEUR GUIDE
Sabetha has a HP of 34 million HP and an enrage timer of 9 minutes (or until the platform gets destroyed). Cannons have 75k HP. There are 4 phases, each triggered every 25% of Sabetha’s HP.
You must have the Explosive Launch mastery trained if you want to go up and do the cannons. Otherwise you don’t need this mastery. This mastery prevents you from taking damage if you get launched off the platform with the Sapper Bombs.
Gearing and Preparation
As usual, full ascended is recommended. Sabetha doesn’t have a big DPS check like Gorseval but every bit helps. Otherwise at least have ascended trinkets and weapons at the least.
Unlike the other two bosses, party composition isn’t as restricted. A tank is not needed here. The fight doesn’t have too much movement so you will be stacked on the boss most of the time. Bring whatever max DPS composition that works for you.
You can either click the special action key or bind it to a button you can press quickly. This is the (-) by default. You need to act quickly during the fight to use this special action button.
You also need to determine which players are going up to kill the cannons and which direction they are responsible. Additionally, those who can deplete a breakbar quickly need to be ready for Knuckles at 50% as that is the only part of the fight that requires breakbars.
For updated Gear/Traits/Builds, check out qT (QUANTIFY)
Phase 1 lasts until Sabetha spawns Kernan at 75% of her HP. Sabetha has several mechanics you need to be aware of.
Timed Bomb is a mechanic that targets the closest person to Sabetha. This person will hear a faint ping and get a bomb icon on them along with a red message in their chatbox. They have a few seconds to move out of the raid. The bomb doesn’t do a lot of damage to that person (2-3k) but if anyone else is caught inside the explosion, they will take massive damage(10k+). Since the bomb has a preference for the person closest to Sabetha, you can have someone like a warrior basically standing inside her while everyone else remain at max melee distance (Sabetha does have a very small hitbox). Timed Bomb cannot be dodged but can be blocked.
If it's your first time on Sabetha and you want to try to avoid getting the Timed Bomb, you can go to your "Options" and scroll down to "Combat Movement" adn put a mark in "Melee Attack Assist". This option prevents you from running through a target, and less chance for you to get the bomb. However, keep in mind later in the fight, that 2 players will get Timed Bomb, so keep an eye out.
Remember to remove this after the raid, as it can be a bit annoying elsewhere.
Flak Shot is a ranged attack from Sabetha on a 7s interval that targets the person furthest away from her. It is a slow moving projectile attack (cannot be reflected) that places a series of fire fields that persists for 25s. Anyone standing in them will receive rapid stacks of burning. To counter this mechanic, you can have someone standing on the outer rings of the platform to kite these fire fields and keep them away from the raid. Since the Flak Shot will target anyone at range, players going up to kill the cannons need to ensure they do not stand on the jump pads for too long or they will get the fire fields placed on them.
Sapper Bombs are green bombs placed on a player by the Bandit Sappers. Bandit Sappers usually spawn right before a cannon in the opposite direction. They tend to target the player closest to them and throw a sapper bomb at them. For example, if you have a cannon in the north direction, a Bandit Sapper will spawn in the south a few seconds before and target someone with the Sapper Bomb. Once you have the Sapper Bomb, you have 5 seconds to aim it at a designated jumping pad in a specific direction to bounce a player waiting at the jumping pad up to the platform above to kill the cannons.
Throw Bomb special action ability has a range of 800 and you only have 5 seconds to act before the bomb disappears. Additionally, if a Bandit Sapper target you once, he will usually target you a second time unless he was killed. So if you missed it once, make sure you are prepared for the second bomb. You will need to know the directions of the four jump pads. It helps to have your commander mark the 4 locations on the mini map.
TacO-overlay is Excellent to use on Sabetha for timers, cannons and directions
If players in your team are spot on with using bombs to boost people up to kill the cannons, you will get extra bombs you can simply throw on Sabetha or the adds. These bombs can deal 30k damage to the adds so it is good to not waste them.
Cannons spawn every 30 seconds in a specific direction with a specific sequence. Cannons are only vulnerable to attacks 8 seconds after they spawn and they have 75K HP health. You can either have 2 players assigned to go to the cannons with a third on backup or 4 players for each of the cardinal directions. Basically anyone other than the Chronomancer or Healer can go up to the cannons to kill them but it is less chaotic if you have players specifically assigned to them. Once a player get launched by a bomb on the jumping pad, they get a Shell-Shocked debuff that prevents them from being launched again for 50 seconds.
You can see which cannons are up by looking at the red swords on the minimap. Cannons will bombard a sector of the platform with AoEs and cause damage to the platforms if not killed quickly. The cannon AoEs are fairly slow but they can do significant damage (10k+) if you get hit by them.
For players killing the cannons, there are bandit snipers up top that will try and attack you but you can avoid their attacks by standing under their platform. You will take some damage gliding down so make sure you heal up before gliding down. There is a small updraft you can use while gliding but you shouldn’t need it. It might be helpful if you see a flamewall coming and need it to pass before landing on the platform.
Cannons start spawning at 8:30, below is a time table with their directions (taken from Lyralei’s spreadsheet). Flamewall timings are not accurate and will depending on your DPS on the champion that spawns.
Flamewall is a rotating attack that starts at 8:30 with a cooldown of 45s. However sometimes she can cast this sooner or later depending on how long you take to DPS the champion adds since she will Flamewall immediately once she returns. It is a massive firewall that will kill anyone caught in it instantly. You cannot dodge through the flamewall or block the attack but you can blink through it. There are a couple things with the flamewall you need to be aware of. The flamewall extends from inside Sabetha all the way to the edge of the platform with a vertical height. This means that if you are standing in melee, you need to be careful to not stand inside Sabetha as you will die instantly. Players gliding back from the cannons need to ensure that they do not try glide over the firewall either.
Sabetha will say Burn. Burn with a chat bubble and sound right before this attack with a huge arrow indicating the start of the flamewall. The flamewall will always rotate counter-clockwise and only does a full 360 deg. Beware of kicks from the Bandit Thug adds that can kick you into the flamewall and kill you instantly. Since you are running in a circle around Sabetha, running closer to her will cut down on the amount of running and allow you to escape her flamewall easier.
In addition to the Bandit Sapper that spawns to give you bombs to destroy the cannons there are two other types of adds as well. Bandit Thugs will kick you which can be deadly if you are kicked into the flamewall or off the platform. Bandit Arsonists will try to flamethrower you which can make you lose your Scholar rune damage bonus. These two adds spawn with every other Bandit Sapper and should be dragged in and cleaved by the raid if possible.
PHASE 2 (75%)
Kernan is the first Champion that Sabetha will spawn. Sabetha will disappear up on the platforms when this champion is summoned and will come down shortly before Kernan is killed (~15% HP but if your DPS is low Sabetha will come down regardless on a timer). There are no Timed Bomb, Flak Shot or Firewall once Sabetha goes up but the Cannons and Bandit adds will still be there. Additionally, there is a new Heavy Bomb mechanic that is present when Sabetha is up in the platforms. Ideally DPS wise you should be spawning Kernan with 7:30 left on the timer.
The main thing with Kernan is her Hail of Bolts which is a succession of 3 attacks, each with a wider angle. The first attack has a 15 deg angle, follow by 30 and 45. If you are caught in the cone, you will receive damage and bleeding ticks. The third attack does the most damage as well. If you are inside or near the first attack, make sure to dodge through Kernan to the other side as she does not change her position once she started doing this attack.
Beware that once Sabetha comes down, she will start her Firewall attack right away! She will always come down when Kernan's HP reach around 25%.
Heavy Bomb is a bomb that spawns frequently near the raid when Sabetha is up on the platforms. It doesn’t do any damage to the player but will deal massive damage to the platform unless removed. To remove the bomb, all you need to do is run up next to the bomb and you will get a prompt to kick it. Kicking it once will remove it. You should have one person designated to keep a lookout for heavy bomb but other players should assist in kicking it if they are close to the bomb.You have 10s to remove the bomb before it explodes and deal heavy platform damage.
Kick it !
Rest of Phase 2
Rest of phase 2 is identical to phase 1. You want to finish off Kernan ASAP to reduce the raidwide damage due to people standing in her Hail of Bolts. Sabetha’s Flamewall attack also rotate a little faster.
PHASE 3 (50%)
Like with Kernan, Sabetha will disappear up in the platforms above once Knuckles is summoned and appear shortly before he dies. The main thing with Knuckles is his breakbar. You must break his breakbar quickly or he will send you up in the air with a knockback. If you are not in the middle of the platform when you get knocked up, it is likely you will be knocked off and killed instantly. You can try and deploy your glider once you are mid-air to prevent the knockback but you need to act fast before the knockback occurs. This is really the only part of the Sabetha fight that requires breakbars so make sure you know who on your team is responsible for them.
Beware that once Sabetha comes down, she will start her Flamewall attack right away! You want to finish Knuckles off as fast as you can to prevent a breakbar as Knuckles can start his breakbar while Sabetha is doing the flamewall. Sabetha will come down when Knuckles HP-bar is around 25%. Unless you have slow DPS.
Rest of Phase 3
The only change in phase 3 from phase 2 is that Timed Bombs now come in pairs, with the second one having a 1s delay. This means that you need to keep an extra eye out for those bombs to ensure you do not blow up the raid. Sabetha’s Flamewall attack also rotates faster.
PHASE 4 (25%)
Like Kernan and Knuckles, Sabetha will disappear to the platforms above when she summons Karde. Karde has a flamethrower attack that deals high damage and will spawn a flame turret every 20s that has low HP. Tempests can place their Lava fonts on the turret to quickly destroy it. The Flame Turret does a slow projectile attack which doesn’t do much damage individually but if you happen to stand on the turret you will eat all of the projectiles and can get downed instantly.
Beware that once Sabetha comes down (when Karde's HP-bar reach around 25%, depending on your dps), she will start her Flamewall attack right away! Platform Crush will also start during the Flamewall attack. You want to kill Karde ASAP as the fight becomes easier once he is dead. Otherwise you will need to deal with his flamethrower attack, flame turrets, flamewall from Sabetha, cannon AoEs and platform crush which can get a bit too much and cause a raid wipe.
Platform Crush is a new mechanic for the last 25% of the fight. You will see orange circles popping up all over the platform. If you stand in them, you will get crushed by a debris falling from above and take massive damage. Sometimes this can kill you instantly as well.
Rest of Phase 4
Once Karde is dead, you will need to keep a lookout for Platform Crush, double Timed Bombs and Sabetha’s Flamewall attack which rotates even faster. You can start ignoring the cannons once Sabetha get to 10% and go for an all out bun on Sabetha. Unless your DPS is really bad or you have a lot of dead players the enrage timer is pretty lenient. However, once Sabetha is enraged she will deal 500% more damage and spawn all 4 cannons so it is impossible to survive.
Some Lulle-art to clear things up a bit
Oopsy Video from Sab 7-man