WORK IN PROGRESS! Lots of guessing and incomplete data. Proper version will take a while because I'm really busy with IRL stuff. If you wish to help please let me know.
You must clear some bandits beforeappears. There are about 30 , and . This is extremely easy and can done even alone. But try to learn their moves to make Sabetha slightly easier.
Arsonists deal heavy damage with their flamethrower but you can just move out of it. Thugs can knock you back. Sappers can plant a bomb on you which deals decent damage. However you can use special action to throw it back at the enemies dealing heavy damage. Throwing it also explodes launch pads which is vital when killing Sabetha.
After about 66% of the enemies are killed you will see the first launchpad. One player must stand on it while someone throws a sapper bomb on it. Keep in mind that you can also launch yourself. The player who gets launched should quickly activate the nearby level to lower wooden platforms. This let's other players come without having to use the launchpad.
There is also onewho is tougher than the rest. His attacks cause a stacking debuff which increases damage taken. However snipers deal so low damage this is nothing to worry about. Clear out the remaining enemies and prepare for the final challenge.
Sabetha stands on middle of an arena surrounded by depths. She won't and can't be moved. In this case Glider Basics isn't strictly required but is extremely useful. Get also Explosive Launch when you can.
The arena is surrounded by 4 platforms on north, west, south and east directions. The arena has 4 corresponding launchpads which can be used to get launched to the platforms. Each platform has a inactive cannon and a.
Cannons peridiocally activate during the fight and have to be destroyed. If not, they will keep bombarding the arena which deals damage to players and may eventually destroy the whole platform. If that happens you will fall to your death.
Using a launchpad places a debuff on you which prevents using launchpads for a while. This means one player can't handle every cannon. The usual tactic is to dedicate 1 player to take care of 1 cannon. Since each of the players has their own cannon everyone knows where they are supposed to be. Alternative tactics are having only 2 persons or whoever gets the bomb goes. Both are very vulnerable to errors.
Sabetha has 3 common attacks. Her basic attack Heat does a low damage on a cone. The damage is quite similar to the auras from other bosses so you need a little bit of sustain to deal with it.
Her ranged attack Flak is more dangerous. It creates multiple ticking AoEs which cause both damage and burning. Standing inside one makes you take lots of damage. This attack will generally target the farthest player so you should have one player at range who moves around the arena.
Her last common attack is Big Bomb which places a debuff at the closest player. After few seconds the debuff expires dealing some damage to self but huge damage to everyone else. When you get the bomb it's vital to move out of the melee stack.
After 30 seconds (8:30) the first cannon appears, other bandits appear and she uses Flamewall. She rotates towards one of the players and places an AoE line after 2.5 seconds. Then she starts rotating anti-clockwise which also moves the AoE. She stops after the AoE has swept over the entire arena. Getting hit by the wall instantly defeats you so it's important to avoid it. It can't be blocked or dodged so you need to move around her or blink over.
You should try to use the launchpad during the Flamewall. This is risky without coordination. Bit before 8:30, everyone should stack at the south side to ensure that Flamewall starts from there. Once Sabetha starts the attack everyone can just sidestep to the left. When someone gets a sapper bomb the wall has already moved past the south launchpad so there is plenty of time.
Firewall will be used every 45 seconds so with the next cannon you don't have to care about it. However the player taking care of the cannon should watch out for the flamewall when he is coming back. With a good DPS you can get Sabetha to 75% and make her disappear before she manages to use Flamewall the second time.
The phase 2 starts withaway. While away, she throws Heavy Bombs at the platform. If they manage to explode the arena takes heavy damage. Interact with them to kick them out of the arena. You don't have to dedicate anyone to do this because there is plenty of time. The player at range should take care of ones in the range while rest take care of the ones close to melee range.
Instead of Sabetha, you have to fight. Her basic attack is a cone which does low damage. After two basic attacks she does 3 cones. The first one has a narrow cone, the second one has a normal cone and the third one has a wide cone. Dodge through if you are going to get hit to avoid lots of damage.
Once Kernan reaches about 15% health Sabetha comes back. She will initiate with Firewall so be ready. Focus Kernan down to reduce pressure. Sabetha behaves exactly same as in phase 1. At 50% health she disappears again.
The phase 3 starts like the phase 2. Instead of fighting, you fight . You should have control against him so make sure your team has some.
His attacks do low damage so you don't have to worry about it. However he gets a defiance bar once in a while. If you don't break it on time he will launch and then knockback everyone out of the arena. This can be avoided by quickly activating your glider but it's safer to break it on time, especially when he gets exposed and takes 50% more damage.
Again Sabetha comes back when "Knuckles" gets low health and initiates with Firewall. The only difference to the phase 2 is that there will be 2 Big Bombs. The second appears about 1 second after the first one. This just means you need to be more focused so you don't blow up your team. At 25% health Sabetha disappears again.
The phase 3 starts like the phase 2. Instead of fighting, you fight .
His basic attack does low damage but his flamethrower does plenty. Just move out of it. Occasionally he summons a?. Focus it down as soon as possible to reduce pressure?
Again Sabetha comes back when Kerda gets low health and initiates with Firewall. The only difference to the phase 3 is that there will multiple delayed AoEs called Platform Crush appearing all around the arena. These deal some damage which adds up to the all pressure.
The most important thing is to take care of cannons. Squads often try to burst her down which means the whole arena gets covered with AoEs. The enrage timer is lenient so play it safe. However if she enrages all cannons appear and she deals 500% more damage so you will get killed really soon.