Queen of the Naga, Empress of Nazjatar, and one of the most powerful entities Azeroth has ever known, Azshara has plotted and schemed for millennia in preparation for this fateful moment. Now, with all the pieces in place, the time has finally come to reveal her end game.
This is a four phase encounter with two intermission phases.
There are three Ancient Wards in the room and a new UI element will show you the status of each of these. It will play a critical role in the encounter.
If your UI does not allow you to move the widget. Import this weak aura: https://wago.io/L5bEdvJqc and move the location of the aura to your desired location
Various abilities in the encounter will deplete the energy of these wards and if they reach 0 energy it will trigger a 
Pressure Surge dealing high ticking damage to the raid.
If all three wards reach 0 energy 
Catastrophic Failure will be cast and you will wipe.
To recharge the Ancient Wards you stand on them, however you will receive the 
Drained Soul debuff which reduces your max health by 10% per stack.
Phase 1
During this phase there are two mini-bosses Aethanel and Cyanus. They do not share a health pool but need to die at similar times, as when one dies the other will get a 65% haste and 150% damage increase.
At set points in the phase the bosses will cast 
Painful Memories or 
Longing.
Painful Memories - Keep the bosses out of Line of Sight of each other
Longing - Keep the bosses in Line of Sight of each other
If this is not completed, the bosses will get the 
Torment buff which increases their haste by 65% and damage by 100%.
Whilst the bosses are active, when they reach 100 energy they will create a pool of 
Cursed Heart under the tank forcing you to move the bosses but you will also need to keep them in or out Line of Sight of each other (depending on which buff they have active).
You are able to stack the pools of Cursed Heart on top of each other if you are keeping an eye out on their energy bar. This is important as these pools will remain for the rest of the fight.
Overzealous Hulk - Throughout the phase this add will spawn and attack an Ancient Ward, this add can be slowed. It will channel 
Ground Pound once it reaches the Ancient Ward which can be interrupted with CC however once it has been CC'd once it will gain the 
Infuriated debuff and be immune to further CC.
Aethanel
Cold Blast - This is the main tank swap of this Phase. You will want to swap when you reach 3 stacks, you will need to utilise a defensive cooldown as the 4th application will make you 
Frozen.
Ice Shard - When you are Frozen you will have this cast on you which deals high Frost damage.
Chain Lightning - This is interruptible.
Lightning Orbs - These will bounce 3 times and then despawn. Avoid these. If you are stood within it you will take a large amount of Nature damage.
Cyranus
Charged Spear - This will deal damage to everyone between the boss and the player. Ensure that you are not in the path of the Spear and that the player ensures the spear travels into the ocean through the outer walls of the room. If the spear collides with a pillar or the console it will deal additional raid damage.
Serrated Edge - This is a stacking bleed but is not the tank swap of this phase.
Azshara
Azshara will be active doing mechanics however you are unable to damage her in this Phase.
Drain Ancient Ward - Azshara will choose one of the Wards and drain energy of it over 5 seconds. This will remove ~50% of its energy.
Beckon - Azshara will cast this on several ranged players and they will be forced to run to the middle of the room for 8 seconds. If they reach the middle of the room they will be encased in a bubble which needs to be killed. The ranged can negate this mechanic by moving to the edge of the room.
Arcane Orb - These will spawn around the room and after 20 seconds they will explode dealing heavy Arcane damage to the raid. However these can be soaked by having players stand within them.
Intermission
During the intermission you will have the Arcane Orbs from the previous phase, and Azshara will give players a Decree to follow. Failing to follow the Decree will apply the 
Sanction debuff which deals heavy Arcane damage.
[Heroic] Each player is given two Decrees to follow.
Suffer! - You must soak Arcane Orbs
Obey! - You should not soak Arcane Orbs (however if nobody else is going to, you should soak it as 1 potential death is better than a wipe)
Stand Together! - Stand with other players
Stand Alone! - Stand by yourself
[Heroic] An additional Decree has been added. 
Stay! - Stand still
Phase 2 (100 - 70%)
When this phase begins Azshara will activate the Rune in the middle and it will become a 
Ward of Power. This will be shown in Blue on the Ward UI element.
As this Ward of Power gains energy it will give the boss and adds increased damage. You can lower the power of the Ward by standing inside of it, however you will get the Drained Soul debuff.
Adds will spawn throughout the phase and move towards the Ward of Power. If they reach it they will die and give the Ward energy. Indominable adds have high health and cannot be CC'd or slowed. Devoted adds have low health but move quickly, these can be CC'd and slowed.
Arcane Jolt - This is the main tank swap mechanic of the phase. Each hit applies 
Arcane Vulnerability.
Arcane Mastery - This is passive damage dealt to the raid over the phase. Will cast Arcane Missiles to all players within Line of Sight.
Titanic Machinations - Which ever Ward the boss is closest to will have its energy drained. If the boss is closest to the Ward of Power its energy will increase instead.
Beckon - This has changed from the first phase and players will be drawn to Azshara instead of the centre of the room. If they reach Azshara they will become mind controlled and will have a large shield applied to them. Remove the shield to free the mind control.
Arcane Burst - This will apply a 30 second debuff to several players. When it expires it will deal heavy Arcane damage to all players in Line of Sight. This debuff can be dispelled, so you will want to have healers run with the players and assign a dispel/movement rotation.
[Heroic] If Azshara is hit by this ability she will gain 
Feedback. If she has this buff it will cause her to cast this on more players.
Arcane Detonation - When Azshara reaches 100 energy this will be cast and deal lethal damage to all players in Line of Sight.
Intermission 2
This plays the same as the first intermission.
[Heroic] An additional Decree has been added. 
March! - This requires you to keep moving.
Phase 3 (Tidemistresses)
In this Phase two Tidemistresses and a Loyal Myrmidon will spawn.
During this phase there are two spawn patterns for the Tidemistresses. The Loyal Myrmidon will spawn in the set areas of the room as denoted by the circles around the central spawn position.
Beckon - This ability has been changed for this phase where it will give players a 10% move speed buff for any players within 8 yards of them via Jealousy.
[Heroic] The move speed increase from Jealousy is increased to 20%
Reversal of Fortune - This is the new ability for Phase 3 and 4. When cast the Ward of Power will swap places with an Ancient Ward.
[Heroic] Azshara gains this ability in Phase 2, and has 
Greater Reversal of Fortune instead in Phase 3 onwards. Greater Reversal of Fortune will swap all Wards of Power and Ancient Wards.
Tidemistress - This add will drain/give the Ward its placed on energy whilst its alive. They will cast Chain Lightning which can be interrupted and will eventually cover themselves in a 
Crystalline Shield which will make them immune to damage.
To remove the Crystalline Shield you will need to hit it with a Charged Spear.
Loyal Myrmidon - Charged Spear - This will target a player and damage anyone in a line from the add to this player.
When both Tidemistresses have died Phase 4 will begin.
Phase 4
In this phase Azshara maintains three abilities from the previous Phases. Titanic Machinations, Reversal of Fortune and Beckon.
Beckon - This has been modified yet again. The speed increase has been increased and if a player is mind controlled they will remain mind controlled and need to be killed.
Nether Portal - Azshara will spawn this near her and standing within it will deal Shadow damage every second. This lasts for 2 minutes so ensure it is not near the Console.
Piercing Gaze - This will target a player and cast a beam in that area. Avoid this.
Overload - This is the main mechanic of the phase and acts as your enrage timer. The console will have multiple charges on it that need to be removed one at a time. Each time a charge is removed the raid will be hit by 
Controlled Burst and a random effect will trigger:
System Shock - This will put a 30 second DoT on the person.
Short Circuit - An Ancient Ward will lose all its power. Players with no or low stacks of Drained Soul will need to move to the Ward.
Essence of Azeroth - A random DPS will gain a 40 second buff which makes all spells instant, increase haste by 50%, and increase resource regeneration. When the buff expires the player will die.
Mythic
All intermissions - New decree combinations are introduced in the fight of Move! and Stand Together!
A new ability 
Divide and Conquer has been added whcih splits the room in two. If you touch the wall you die.
Phase 3 - 3 Tidemistresses will spawn (up from 2)
Phase 4 - Divide and Conquer will rotate when it spawns making it more of a threat.
Phase 4 - 
Void Touched - This is the tank mechanic of this phase. Swap after the debuff drops. Each stack reduces healing received by 10%.
This fight on Mythic is very structured in how you approach it with fixed push timings, with this in mind we are able to note down how to handle each part of the fight.
On the pull stack both bosses on the Aethenil position as denoted on the map above
When there is around 4-5 seconds remaining on Painful Memories the Cyranus should move the boss to the new location and start to stack every Cursed Heart puddle on a single location.
Cursed Heart puddles spawn when the boss reaches 100 energy, if they are casting at the same time the puddle will spawn underneath them, if they are not it will spawn under the tank. Therefore you will need to move into the existing puddle to stack it.
At this point the first Hulk will spawn. If you are using the Cyclotronic Blast trinket, cast it on this Hulk.
After this Arcane Orbs will spawn, if one spawns near you soak it.
Aethenil Tank - Each time you get frozen ensure you have a defensive cooldown up. If none are available, use externals. it doesn't matter if you feel safe or not, use them.
Cyranus Tank - When the first beckon cast happens, use your defensive cooldowns here, healers are spread out and one is in beckon.
After the Arcane Orbs are finished, Cyranus will do one last spear and at this point they will cast Longing, bring Cyranus to the Aethenil position for 2 Cursed Hearts. After this move him back.
Hold the bosses until the next Arcane Orb and half way through their soak kill the bosses. Ensure Cyranus does not cast a spear during this set of Arcane Orbs. Kill him before the cast finishes if it starts.
When the boss becomes active use your Cyclotronic Blast trinket and start to hit the boss.
Drag the boss to the middle of the room and keep her there.
The adds will now spawn and move towards the middle, it is important to keep the boss in the middle here, to ensure that DPS get free cleave damage onto the adds. When they reach the middle you should have an assigned stun + knockback. These adds are not a high priority to kill, just manage them and they will die from DoTs and Cleave.
If you have a blood death knight, mass grip the adds when they reach the middle after the stun towards the console.
When the beam spawns you want to move the boss to the left side of the console. You want the boss to be a little bit away from the console than directly hugging it to allow Ranged DPS to still hit the boss when they are soaking the ward. (As shown in the map below)
After 3 jolts on the main tank you will swap and hide behind the console to drop your stacks.
Whilst hiding ensure you are not LoS of the boss and are not going to be hit by the Arcane Bursts as these will refresh your stacks.
When your debuff runs out swap on the boss and allow the other tank to hide.
This phase is the majority of your progress + encounter time. Your strategy will denote how you handle this phase so I will only explain the core concepts and how the mechanics work in some detail.
If this is part of your strategy, how you handle this is you start off the phase with both tanks on the boss at the console. You do a few globals into Venomtongue (Double Crucible of Flame + Cyclotronic Blast and move when Cyclo is channeling).
You will then move behind the pillar and as both tanks are the only targets in Line of Sight of the Myrmidon it will cast on one of the tanks.
The Myrmidon will only cast on people in its Line of Sight.
The add spawned by the beckon will go on set locations in the room. However it can only go on a space that is not occupied by the boss and is the closest to the boss.
Therefore, in the image below as an example if the boss is tanked in the spaces 1 and 2, the beckon add will spawn on location 3. However if the boss was moved slightly away from location 2, it will spawn in location 2.
This piece isn't really tank specific, but I thought it was important to share. In Phase 3 there are 4 beckon casts in total therefore the use of warlock gateways are only required on Beckon 1 and 3.
Beckons 2 + 4 have no beam in the room, so you are able to move a bit further out and run towards the console if you get the beckon, thus saving yourself from having the gateway cooldown if you are unlucky enough to get Beckon twice in a row.
With this in mind, players with blinks/disengages/teleports can use them here (example of warlock teleport shown on the image above), other players without this utility will simply run.
Generally you want to be swapping on each spear cast and when your debuff stacks have dropped, this allows for easier swaps. You swap by having the Myrmidon tank come to Azshara and taunt (so she doesn't move much) and then swapping at that point.
Generally you want to keep the Myrmidon further away than necessary to make spear aiming easier.
In this phase you will start with the boss at the pillar still and she will stand still and channel. Your raid will have a warlock gateway set up as shown below.
When the first Nether Portal is cast your raid will move to the console and do the first round of clicks. (Be sure to have the raid reset stacks, tanks don't really need to reset stacks this phase)
Next you will have the beam spawn. If it is on the opposite side of the console, move to the other side.
After this you will have Piercing Gaze happen, 4 of these will happen in quick succession. When this is done, follow the direction of the beam to the pillar.
Your DPS will LoS on the pillar to drop their stacks. After this ranged will bait the Nether Portal against the wall and stack on the boss.
Once the Nether Portal has been cast the raid will then stack on the boss.
Keep the boss away from the beam ending points. You can denote these by the raised areas on the edge of the room as shown on the map below.
After this you will be going back to the console for your 2nd console clicks.
You will then have your 2nd set of Piecing Gaze, however during these you will want to go back to the side you placed the previous Nether Portals. As after the last Gaze the Portal will cast.
Return to the console at this point and avoid the end of the next beam. If you are clicking reset stacks + click, if you are killing the boss just burn it.
Phase 1 - Utiise a defensive on 3 stacks of Cold Blast (before the 4th stack applies)
Phase 1 - Keep the boss in/out of Line of Sight as required
Phase 2+3 - Swap on ~7 applications of Arcane Vulnerability
[Mythic] Phase 4 - Swap when Void Touched expires
Ideally in Phase 1 you should be taking Cyranus as the Serrated Edge bleed will not apply if you dodge
Utilse 
Ring of Peace to keep the Devoted adds from reaching the Wards
Utilise 
Sigil of Chains to keep the Devoted adds from reaching the Wards
You can utilise 
Blessing of Spellwarding to prevent stack gain of Cold Blast, Arcane Vulnerability, and Void Touched
You can cast Blessing of Protection on a player with Beckon to remove the effect whilst they are under the forced movement effect
You can utilise 
Blessing of Sacrifice to reduce the damage taken on your co-tank in Phase 4
You can utilise 
Intervene to reduce the damage taken on your co-tank in Phase 4
You can Deflect the Arcane Missiles from the boss with 
Spell Reflect
You can Reflect the Arcane Vulnerability debuff and give the boss the damage taken increase with Spell Reflect
Utilise 
Typhoon and 
Ursol's Vortex to keep the Devoted adds from reaching the Wards
Use 
Stampeding Roar to help the raid move large distances to get to the pillars for Line of Sight breaking
You can utilise 
Anti-Magic Shell to prevent stack gain of Cold Blast (this is best used to negate the 4th stack), and Arcane Vulnerability
Utilise Grips to keep the Devoted adds from reaching the Wards
You can Mass Grip all 3 sets of the Devoted adds together at the edge of the centre ward (if they have not been slowed) to allow for quick AoE