Not calling this a guide, making it more tips than anything. But I figured with most likely only today after the fate issue being fixed attempting this, a bit of inside info couldn't hurt.
Contrary to the name and the presentation of the entire place, it's actually linear, there is zero choice in the path you must take.
Take the 1st left and start following the path. Don't let the Teleporter messages confuse you, all those do is provide a shortcut to the newest activated.
The first 3 rooms you'll come across will close off behind your group, but it really is just slightly stronger trash mobs, they can be pulled separately, no need to aggro the whole groups. Inform your tanks of this if nobody is aware yet.
After clearing this, you'll reach the first boss, the Bone Dragon.
He has extremely little health but one of the nastiest gimmicks yet. As his health drops, he summons skeleton adds. Do NOT simply kill these when they spawn. Have your tanks pull them as far away from Bone Dragon as they can, and ALSO as far away from each other as possible. The arena is big, so this just requires coordination among players. Once they're in position, kill them all before doing the finishing blow to the Dragon.
Once the Dragons HP drops to 0, he'll go unconscious, and all the Skeletons rise again. They won't attack now, they'll merely try to run to Bone Dragon's location. If they reach him, massive unavoidable AoE. 2 of those AoE's in succession will wipe most non tanks, 3 will wipe you for good. This is why they needed to be separated, they gain a speed boost if they're close to other skeletons. 2 skeletons resurrecting right next to each other move towards BD at sprint speed. Solo skeletons suffer a Heavy effect and can easily be dispatched.
Once this has been survived, BD gets back up, and you repeat that pattern one more time. After he gets up again, all he summons is Eyes. These can either be killed or flat ignored in favor of burning the boss down, up to the party.
Congratulations, the 1st gear chest is yours.
Moving on, you'll go back to the start and head to the East side. No trash here, only the most complicated miniboss you've likely encountered. There will be 3 lanes, left, middle, and right. Have alliances A, B, and C get in position in one each. Make sure nobody crosses the purple line for the enemy behind it draws aggro easily.
Everyone's Atomos sits on a colored platform. Normally, Atomos is invincible, to remove his shield, the correctly colored platform must be activated by having at least 4 players stand on it. Alliance A has the platform to allow for the removal of Atomos B's shield, B has C, C has A.
Atomos does not attack, but there will be a constant stream of adds.
All that needs to be done is assign 4 players in each alliance to stay on the platform. Those players must remain there at all times.
There's a condition that causes an overpowered Iron Giant to spawn. Currently I am unsure what triggers this, hard to test it with a guaranteed 16 people I have no influence over. Let me know if anyone finds out.
Next Boss, Thanatos.
The area contains 3 magic pots which are your allies. Thanatos is invincible normally. The magic pots cast a spell on an alliance at a time that turns all of its members ghostly. These are the only characters able to fight Thanatos as long as it lasts. Everyone that isn't ghostly is on duty to kill the dozens of adds that try to kill the Magic Pots.
This one really is simpler than I can make it sound, all it boils down to is, fight Thanatos if your alliance is allowed to, wipe adds otherwise. Make sure the Tanks provoke thanatos away from the previous alliance so he doesnt chase a tank that cant defend themselves after losing the ghostly status.
After Thanatos' demise, 2nd gear chest is yours.
Moving on, back to start, now the center path.
You'll come across another miniboss that's harder than most bosses.
3 Vassago, 1 bomb in the middle. The bomb cannot be damaged at first. Each alliance gets 1 Vassago and starts work on that, keep them at the edges. Periodically, adds spawn. Kill the Balloons since they'll come for you, and more importantly, kill the Napalms, ASAP. The napalms don't fight, only hover over to the center bomb. If they reach it, it grows. After a few Napalms reach the center bomb, it'll explode, wiping the entire party. So don't let the Napalms get that far.
If your Vassago starts taking next to no damage, just keep at it, they get a damage reduction effect any time the big bomb looks that way, just gonna have to live with that since pulling the vassagos all over the room is not worth it.
Moving on to the toughest boss. Expect to wipe to him a bit.
He's a piece of work. Entire area is electrified, so all members take slow and steady damage throughout. There are 4 towers at 4 corners, have a tank positioned on each of these. Their duty is to interact with their tower each time it starts glowing red to shut it back down. Allowing these to charge will power up the electricity, causing the party to go that much faster.
Constantly, adds spawn at the center that make their way for the towers. Kill them. Destruction of tower controls means you can't shut them down anymore.
Periodically, KB will drop Comets. This is indicated by a green marker on your character if you're being targeted, which happens randomly. Do NOT try to run from this, it's unavoidable. Instead, make sure you go to the center of the arena. If you're one of the designated tower guards, don't go all the way to the center, but do make sure the comet lands closer to the center. You'll need it.
Because, at times, KB will get up on his hind legs, you'll get a "Graaaaaaagh!!" message, and he begins casting Meteor. This cannot be prevented. Only way to not die is to hide behind one of the comets, get one of those between you and KB's location and you'll take no damage.
That's all the mechanics going for this guy, the issue is in the numbers. It's all very spot on, all 24 players must pull their weight, the numbers are not in your favor here, everything hurts bad and the adds have a good amount of health.
If you win, Congratulations! 3rd gear chest is yours.
Next up is immediately the final boss, Acheron.
Coming from KB, he's significantly easier to handle but by no means a pushover. Make note of the Runed circle as you enter the arena. There are 3 rings that you'll need to reach at some point, so designate one for each alliance.
Normal battle is simple here, he casts several AoE attacks with new patterns, so do your best to evade. The only move that can't be avoided is Quake III, which does around 70% damage to everyone, so gotta power the heals at that point. Occasionally adds will spawn, rid them as you go.
Now, the gimmick. After a while he will begin casting Ancient Flame (or at least I think that's what the name was). RUN and I mean RUUUUN to your designated ring and trigger it by standing on it. If all 3 rings are triggered, a protective barrier seals Acheron off from everyone, preventing the move from killing you instantly.
An Iron Giant and other adds will spawn at that point, only after killing them does the damage field at the center go away. Once it does, resume battle in this fashion until he is dead. On my successful run he attempted Ancient Flame no more than twice, but don't let your guard down.
If you win, congratulations! 4th gear chest is yours, and you've completed crystal tower, for now.