This page explains how to complete the level 90 post-Endwalker duty, Alzadaal's Legacy.
On the Way to the Undersea Entrance
On the way to the first boss, there will sometimes be circle attack markers that have curved lines of arrows pointing to them. This indicates that enemies will appear in the marked locations.
Big Wave damages all players and inflicts all players with Bleeding status, which cannot be removed with Esuna.
When the boss casts Tentacle Dig, it will put a tentacle underwater, and the path of the tentacle can be seen on the surface of the water. It will move in a curving path before stopping in a random location. There will be a very large circle attack originating from where the tentacle stops, so all players should move away from that location as soon as possible. Because of the short amount of time to get out of the circle attack marker once it appears, players may wish to keep their distance from the tentacle path the entire time that it is moving.
This is followed by another Tentacle Dig, this time with both tentacles going underwater and emerging in a random location.
Toxic Fountain places many circle attack markers in the area, followed by another set of circle attack markers, causing the entire are to be covered. Take note of where the first set appeared, and stand on one of the second set, so that you can move into the safe area left behind when the first set disappears.
On the Way to the Threshold of Bounty
On the way to the second boss, you will encounter Alzadaal's Ramparts, which will tether to the watery walls and repeately cast Reinforcements, summoning more and more enemies. Focus all attacks on the Alzadaal's Rampart to destroy it as quickly as possible and minimize the number of enemies that you have to fight.
The boss will start by placing a circle attack marker beneath itself, and that area will become a damaging area that you will need to avoid for the duration of the battle.
Articulated Bits summons untargetable Death Claws at the edges of the area. The claws will have numbered indicators above them, indicating that two of the claws will attack first, then the other two will attack second. At the same time, the boss will place reflecting shields around itself. As a result, each time a Death Claw attacks, the quadrant that the claw is at the corner of will be hit with an attack. Go to a quadrant that has a claw with a "two" indicator at the corner, then when the first attack is done, move to one of the quadrants where the attack just occurred.
Diffusion Ray damages all players.
The next time the boss casts Articulated Bits, there will be corner Death Claws as well as Death Claws facing forward. The claws that are facing forward will do a line attack in the direction that they are facing. Instead of having numbered indicators above them, the Claws will attack at the same time. Don't be in a quadrant with a Death Claw at the corner, but also make sure not to be in front of any of the Claws that are facing forward.
Graviton Cannon marks all players with circle attack markers that follow them. Players should spread apart from each other to avoid overlapping each other with their circles.
Rail Cannon is a high-damage attack on the player highest in the enmity list.
At the beginning of the battle, spikes will be raised around the edge of the area. Avoid the spikes or you will take damage and be inflicted with Stab Wound status, which cannot be removed with Esuna.
Billowing Bolts damages all players.
Spin Out will place square attack markers in the area where spikes will appear, and all players will be pulled toward the boss. The players will then have hand indicators above their heads and will move in the direction that the hand is pointing. Players can't stop their movement at this time, but they can change the direction of the hand. However, changing direction does not happen immediately, so you will need to continually aim yourself to avoid moving over the spikes around the edges and the other spikes in the battle area.
Crewel Slice is a high-damage attack on the player highest in the enmity list.
Wild Weave causes different colored fabric to hang down from above, and the boss will cast Power Serge, tethering to a certain color fabric. Each piece of fabric that is the same color as the tethered fabric will have a brief circle attack marker around it. As soon as the boss tethers to the fabric, stand under one of the pieces of fabric that is not the same color as the tethered fabric.
Rotary Gale marks all players with circle attack markers that follow them. Players should spread apart from each other to avoid overlapping each other with their circles.
Later, when the boss casts Spin Out, it will dash to the edge and cast Basting Blade, a wide line attack across the area in the direction that the boss is facing. As soon as you see the boss dash to the edge, begin aiming your spinning character away from the area that the boss is facing to avoid the line attack.