Heya. I know a lot of people hate this dungeon so I figured I'd post a guide to help a bit.

Boss #1: Symond the Unsinkable
- Tank tanks on the wall.
- Don't tank adds. They help with the Corrupting Spit attack that gives a Corrupted Crystal debuff. Do not allow it to build up to 3 stacks. If anyone gets 3 stacks, they'll die. Corrupting Spit has next to no warning, as well, so healer and DPS need to be ready to move.
- There's a big yellow ground called Crystaline Shot. You'll get a debuff from being on it so be wary of that.
- Adds need to die ASAP, so all DPS should go focus on them.
- Boss gains Giga Slash around 30%. It does a knockback effect, so if the tank's on the wall it won't have much of an effect on that end.
- The trick to this fight is ironically slow DPS. If you get the HP down too fast, you'll cause more adds to spawn as they appear based off HP % (if you do too much damage, you'll get more adds) so take it slow and steady.

Boss #2: Zu
- There's no "slow DPS" check here, so you can fight it as a DPS race.
- The first thing you'll notice is that there are a ton of eggs around the arena.
- Do NOT destroy them unless you have to. Two eggs will threaten to hatch. Killing one egg gives Zu 8 stacks. If you kill two eggs and build 16 stacks, Zu gains a massive damage attack that'll do some extreme damage to tanks and DPS alike. So do NOT kill more than one egg at a given time. When Zu's 'rage' calms down, you can worry about killing another egg by that point. Again, can't stress it enough: never allow it to build 16 stacks.
- Zu's basic attack is a frontal AoE attack, so the tank needs to keep Zu in one area, preferably in the middle. During portions of the fight the Zu will go up in the air and target the person with the highest hate (usually the tank) and it will do three AoE blasts centered on that target. This calls for a simple simple dodge asap reaction.
- Other than that, tank and spank. Tank doesn't need to grab adds, they'll die fast with DPS focused on them.

Boss #3: Tyrant
- This boss is a pure DPS race, tank and spank it! Avoid the adds if you can. This is by far the easiest boss. You should have no issues downing it while avoiding adds, but if you have to, do it.

Final Boss: Siren
- Okay, Siren's a bit tricky. Skill will be put to the test here as well as luck. It's a healer test here.
- Siren will spawn adds. If you see any Sergents, kill those first. Otherwise, kill adds asap. If the Sergents reach the person they have hate on, they will stun them and the effect will not wear off until they are killed.
- Song of Torment grants a bleeding effect on the person it's used on. Esuna/Leeches it asap.
- Lunatic Voice is a healer's worst enemy in this fight. Grants Reduced Immunity on all party members, so it's very important to react as fast as possible to this.
- Siren does two charm attacks. One is single-target called Dreamy Voice which grants a debuff on the target. If you don't eliminate it, the person will get charmed. To cure it, cure the target's HP to 100%. The other charm attack occurs when Siren jumps into the air and appears in the center of the room. She prepares the attack during that (think Hydra's "Fear Itself"). Everyone needs to be in the center ASAP or everyone away from it will get charmed. This would be the healer's second worst enemy in this fight, because it won't be very feasible to cure everyone if they get hit. If it does happen, the healer should definitely prioritize them and the tank (although the tank shouldn't get hit by the AoE charm). Due to this reason alone Siren should be tanked in the center of the room. The other attack Siren does while going in the air is a dash much like Ifrit's Crimson Cyclone.
- In the event the healer gets charmed, tanks should use their critical defensive cooldowns. Hopefully, this won't happen and it shouldn't happen.
tl;dr: Healers need to heavily focus on the reduced immunity debuffs and solo charms. If healers have hate on the adds, move to the tank. This will require more healing during that phase. If healer gets charmed, tank should be ready for it and react accordingly. Kill sergeants as fast as possible and prioritize those over the other adds. Get in the center as soon as Siren jumps and appears there. Avoid the dash. Other than that, tank and spank.

Tsu Notes:

Symond: Corrupting spit really has basically no warning - you pretty much have to already be moving. Crystalsplosion is survivable, at least as a DPS. Be aware that his Crystaline Shot ground AOES will grow in radius twice before they disappear - you're not safe just because you're out of the red area, and if you're on the far side from the tank, you'll be crowded out of range of the main fight entirely.

Zu: There are two kinds of eggs - white and speckled. White eggs spawn pullets, speckled eggs spawn cockerels. Pullets are just DPS; cockerels have a ranged HP/MP drain, kill them first. If you have a choice of which egg to break, choose the speckled one. Choose a DPS who will be breaking eggs; it can get bad if both of them choose one =P

Tyrant: A joke boss. I've had groups just assign the healer to kiting duty and burn him down before anyone dies.

Siren: There is a metal border around the central circle of the room. When Siren flies, up, stand on the metal circle - you'll have a better chance of dodging a dash attack, and if you see her come down in the middle you'll have time to run to the safe zone. She seems to do AOE charms way more often than dash attacks. Sergeants will always have hate locked on the healer or tank; focus on ones going for the healer first.

Thank you for this! :) Good stuff!

Also, you can silence "Lunatic Voice"