Priscilla Ashvane's relentless pursuit of power has ultimately led her to the Eternal Palace and into a dark pact with Queen Azshara. But what Ashvane receives in return for her loyalty may be more than she bargained for.
This is a two phase encounter where in Phase 1 you will focus on breaking the boss shield and maximising available space in the room, and in Phase 2 you will clear the space and deal damage to the boss.
Phase 1
Hardened Carapace - The boss will have a shield for 40% of her health. Once this shield has been broken Phase 2 will begin. Every time the boss returns to Phase 1 the shield will be 150% stronger.
Barnacle Bash - This the main tank swap mechanic of the fight and the debuff will make the tank take 150% more damage from it for 35 seconds. This can stack and there are scenarios where the previous debuff would not have fallen off in time, if this happens be ready to adapt and use a cooldown.
Each cast of Barnacle Bash will spawn 
Cutting Coral which will deal damage to any players within it. After each cast you will want to move around the edge of the room to maximise encounter room.
[Heroic] Cutting Coral does not despawn.
Coral Growth - Per cast two Corals will spawn in the room. Each of these Corals will trigger when the boss casts Rippling Wave.
[Heroic] Three Corals will spawn each cast.
Rippling Wave - Every Coral will spawn a bubble. If the bubble reaches the boss up to 10% of the shield will be restored. Players can intercept the bubbles however each soak will deal raid wide damage and the player who soaked it will receive the 
Waterlogged debuff (this stacks).
Upsurge - This will spawn on the locations of several players in the raid, and shortly after knock any players within this area into the air. Move out of these.
Briny Bubble - The active tank and two DPS players will get this debuff and shortly after have the bubble surround them. Whilst they are in the bubble they will take Nature damage every 1.5 seconds.
[Heroic] Anyone within 12y of the target will become a bubble.
Phase 2
During this phase the boss no longer casts Coral Growth or Rippling Wave in this phase.
Arcing Azerite - The boss will link 3 sets of players together with a clear visual indicator above the heads of the players. After 10 seconds any people between the players will take heavy Arcane damage, and any Corals between them will be destroyed.
Exposed Azerite - This deals Arcane damage to random targets periodically throughout this phase.
The boss will renegerate energy, and after 1 minute and 10 seconds Phase 1 will begin, however the shield will be stronger making Phase 1 last longer each time.
Mythic
Empowered Rippling Wave - The Coral furthest from the boss will have an empowered bubble. This bubble needs to be soaked three times to despawn.
The Waterlogged debuff lasts 20 minutes (up from 15 seconds) meaning that you will need everyone to be involved with soaking at some point in the fight.
Regenerative Coral - When a Coral is destroyed in Phase 2 several soak circles will spawn. If they are not soaked a new Coral will spawn.
Swap after each cast of Barnacle Bash
Try and maximise the space by keeping the boss close to previous patches of Cutting Coral
If a Coral spawns close to the boss in Phase 1, move it away to prevent healing
The minor essence from Nullification Dynamo is powerful on this fight if you maintain 1 stack of Waterlogged as it will proc the shield off cooldown giving you an extra boost of DPS (~2k DPS).
[Potential Bug] Whilst you are encased in a Briny Bubble, some non targeted spells continue to function as normal.
The speed boost from 
Provoke can be useful to move the boss from Cutting Coral patches
Tiger's Lust is available for all Arcing Azerite casts and can be used to cover large distances
Infernal Strike can be used to cover large distances when you are affected by Arcing Azerite
Divine Steed can be used to cover large distances when you are affected by Arcing Azerite
You can soak multiple Rippling Waves with 
Blessing of Spellwarding and 
Divine Shield
Barnacle Bash can be blocked
You can break out of the Briny Bubble with Divine Shield
You can break out of the Briny Bubble with Divine Steed if you have the Conflict and Strife essence Major.
Heroic Leap can be used to cover large distances when you are affected by Arcing Azerite
Barnacle Bash can be blocked
You can break out of the Briny Bubble with 
Berserker Rage
Stempeding Roar, and 
Dash can be used to cover large distances when you are affected by Arcing Azerite
You can soak multiple Rippling Waves with 
Anti-Magic Shell
Wraith Walk can be used to cover large distances when you are affected by Arcing Azerite
You can pevent Briny Bubble from forming with Anti-Magic Shell