Where: Your best bet for finding this boss is playing through the Corsus area in Adventure mode. Her dungeon is called Iskal Temple. It does not spawn every time so reroll if you play through and don't see it.
How: This fight is split into two distinct phases. Arguably the toughest part is the first phase. The Queen will be at her throne at the back of the arena. Your objective is to remove approx 1/3 of her health bar to trigger the second phase. The Queen will then descend down into the center of the room for the remainder of the fight.
For the first phase, you will have to deal with quite a bit. She spawns bugs, waves, and splash bombs. You have to deal with each of these while also dealing damage when you can.
Once you've done enough damage, the boss will hop down from her throne. Make sure you are reloaded immediately when she does this. She will temporarily freeze you in place, the arena is covered in mist and your character will cough. As soon as you are able, you must DPS her head as much as possible to stun her before she reaches you. If she does reach you, it will most likely be a one hit kill.
[(EDIT: ALT KILL) As soon as you've begun the second phase, you shoot her in the head to stun her. If you can do this in the center of the room directly below one of the hanging yellow masses - as soon as she is stunned, look up to the ceiling and shoot the yellow stalactite and it will drop on her and kill her. This is harder than it sounds. The boss must be precisely below otherwise it will miss.]
From here, the boss will not spawn any adds, but summons an axe that she will attempt to melee you with. She can also shoot beams from this axe as well. Dodge rolling is crucial in this phase. Her attacks are tough to time, but once you get the feel for them you should be able to avoid most of them.
Once she is down to her final 1/3 of health, the boss will rise up into the air and launch beams that you can roll to avoid as well. This part isn't a whole lot different from the previous. Keep dodging and attacking when able.
Gear & Tips: Just about everything in this boss fight deals corrosive damage, mainly in the first phase. I highly recommend stocking up on Greenleafs and Bloodwort consumables to combat this. The Cleansing Jewel (Amulet) can be a big help as well, since it will rid status effects upon using a dragonheart.
Light armor makes the second phase more manageable. I was struggling with my Radiant set because I couldn't roll away fast enough from some of her attacks. Once I switched to the Akari set I faired much better.
(personally I used repeater pistol with swarm mod, beam rifle with hot shot, akari set, cleansing jewel, devouring loop, and stone of balance)
General Strategy: Kill the bugs. Always keep an eye on her wings/staff to know when the waves are coming. Stay in the middle, unless she raises her staff, then roll to one side. Roll away from splash bombs. Damage until she leaves her throne. Stun her by shooting her head. Dodge roll her axe. Profit.
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That's it really. If you're still struggling... I'll break down how the first phase usually goes because that's where I struggled the most. She has 4 main moves and typically uses them in a certain order. Bug Spawn, Corrosive waves, Splash Bombs, and a BS explosion.
Her moves: (1 - Bug Spawn) The fight starts with the Queen summoning bugs that crawl toward you on the ground. They start from below where the Queen sits. Position yourself far enough back in the room to give yourself space to clear them out before they get to you and explode. They deal corrosive damage. If you can shoot ones that are close together you can take multiple bugs out in the explosion. There will typically be two waves of bugs whenever she spawns them.
(2 - Corrosive Wave) The Queen has two different wave attacks she will send along the ground toward you. These waves do a lot of damage and should be avoided at all costs. The first type is one wave that travels directly down the center of the arena. This one is telegraphed fairly obviously with the Queen raising her staff moments before the wave is released.
The second type is 2 waves that travel down the left and right side of the arena at the same time. You are safe in the middle of the room. This one is a bit trickier to spot. Her tell is that her wings will glow bright blue when she is going to use this move. However, a lot of the time the wings will glow and she will do a different attack first, but sure as sh*t, those waves are coming shortly after, so try to stay in the middle as best you can.
(3 - Splash Bombs) This move really isn't so bad but if not avoided it can be deadly. Similar to Ixillis (the boss on the bridge), the Iskal Queen lobs these corrosive bombs at you. Almost always it will be two of them consecutively. These can easily be dodged by rolling. Not a whole lot to this move.
(4 - BS explosion) I call this one the BS explosion cause its bullsh*t. The boss spawns a single bug that appears on your own wrist. When the boss snaps her fingers, the bug explodes, damaging and staggering you. I just tried to stay healed up/used a bloodwort when I knew it was coming. UPDATE it is actually possible to avoid this damage. There's nothing you can do about the bug itself, but when she snaps her fingers together you can roll at that exact moment to avoid the damage, but it's a very small window. Cheers.
