The third boss in the Bastion of Twilight, the Ascendant Council is a group of four Elemental Ascendants. They are fought in pairs; Water and Fire, Earth and Wind. This fight is reminiscent of Omnitron Defense system in that you must manage the gimmicks of two bosses at once, however this fight has a brutal third phase which is influenced by how you manage the Ascendants in phases 1 and 2. 

Abilities

Phase One 

Feludius (Water) 

• Heart of Ice - Deals periodic frost damage to the target. This effect is dispellable. If the target is not dispelled and comes in contact with other raid members they will deal massively increased damage to Ignacious.
• Hydrolance - A lance of ice that deals 50,000 damage to a random target. This is interruptable.
• Waterbomb - Splashes water on areas of the ground hitting everyone within 6 yards for 10,000 and giving them the 'Waterlogged' effect.
• Waterlogged - Slows enemies by 25% and freezes them if they do not removed the effect. This effect can be removed by walking through Ignacious' fire.
• Glaciate - Charge up effect that deals massive AoE frost damage. This emanates from Feludius and must be avoided.
• Frozen Blood - Freezes a Waterlogged player dealing damage over time. 

Ignacious (Fire) 

• Burning Blood - Deals periodic Fire damage to a player. This effect is dispellable. This acts like Heart of Ice in that players nearby the effected player will gain massively increased damage against Feludius.
• Aegis of Flame - Ignacious places a shield on himself that absorbs 1,000,000 damage and makes him immune to interrupts.
• Flame Torrent - Frontal cone AoE fire attack.
• Inferno Leap - Ignacious leaps at a ranged enemy dealing 25,000 damage and knocking back nearby players.
• Inferno Rush - After Inferno Leap Ignacious will rush back to the tank leaving a trail of fire in his wake. This fire removes Waterlogged.
• Rising Flames - Massive AoE fire damage attack that increases in strength. This effect is interruptable but is used in concert with Aegis of Flame, so interrupts will be dependent on breaking the Aegis. 

Phase Two 

Arion (Wind) 

• Call Winds - Creates a tornado that moves randomly about the room. This tornado will levitate players that walk into it.
• Lightning Rod - Marks a player with an arrow which indicates that they will be targeted with Chain Lightning shortly thereafter.
• Chain Lightning - Shoots lightning at a player which will link to nearby players dealing massive damage.
• Disperse - Arion teleports to another location in the room.
• Lightning Blast - Attacks the tank with lightning for 80,000 damage after Disperse is used.
• Thundershock - Charge-up ability. Deals massive room-wide damage which is more effective against levitated targets and less effective versus grounded targets. 

Terrastra (Earth) 

• Gravity Well - Creates an effect on the ground that will pull players towards the earth. This gives the 'grounded' effect that is used to mitigate Thundershock.
• Gravity Core - Deals damage over time to players that enter a Gravity Well, also decreases movement speed of nearby players.
• Harden Skin - Increases Terrastra's damage dealt by 100% and reduces incoming damage by 50% up to 650,000. When this barrier is broken Terrastra will take massive damage.
• Eruption - Creates an effect on the ground which will erupt after a short period dealing 50,000 damage to players standing nearby and launching them into the air.
• Quake - Charge-up ability. Deals massive room-wide damage which is more effective against grounded targets and less effective versus levitated targets. 

Phase Three 

Elementium Monstrosity 

• Lava Seed - Sprays fire about the room that appears on the ground to look like flares. They will explode in gouts of lava after a few seconds.
• Liquid Ice - Spawns a pool of ice beneath its feet which deals damage and expands when the boss stands in it.
• Electric Instability - Deals nature damage to random ranged targets that increases for as long as the monstrosity is alive. This ability chains to nearby targets.
• Gravity Crush - Lifts enemies into the air hitting for 10% of their health every 0.5 seconds for 6 seconds. The targets will drop to the ground after the effect ends and take fall damage. 

Setting Up 

Tanks: 2
DPS: 5
Healers: 3 

Since phases 1 and 2 have two bosses active at once you're going to need two tanks. The healing on this fight can get quite extreme, so you'll need three healers as well. Due to the chaos and ramping damage in phase 3 it is an intense burn phase that will require 5 DPS to beat in time. This set up isn't really negotiable for learning this fight. 

Tactics 

The list of abilities that you need to know for this boss is intimidating for sure. It makes Maloriak look like a boss in a 5 player dungeon by comparison. The good part is that each of the three phases is basically a self-contained fight so you'll be able to learn them one at a time. The bad part is that this fight is as tricky as it sounds in many ways. 

There is a gimmick that must be obeyed to beat this boss, and that gimmick is how the hit points of each boss in phase 1 and 2 influence the  hit points of the phase 3 monstrosity. Basically the transition from phase 1 to 2 and 2 to 3 is triggered when one of the bosses  reaches 25% life. At the beginning of phase 3 they will all merge together and will add their hit points together. This means that you are going to want to have Feludius and Ignacious pushed to 25% at the same time in phase 1, and likewise for Terrastra and Arion in phase 2. 

The fight will begin with melee and a tank on Ignacious and the ranged DPS and another tank on Feludius. On normal mode healers should feel free to dispel Burning Blood and Heart of Ice because they aren't really necessary or even that helpful for learning this fight. When Ignacious casts Aegis of Flame the ranged DPS need to switch to him to help the melee break the Aegis quickly, interrupt him once the Aegis is broken. Raid leaders should monitor the hit points of each boss and balance DPS accordingly. It's important to remember that when you are affected by Waterlogged you need to walk through Ignacious' trail of flame. It doesn't deal too much damage and is better than being frozen! The majority of damage in this phase is avoidable. Don't stand in melee range of Feludius when he casts Glaciate and make sure that Ignacious is faced away from the raid so his cone of fire doesn't hit anyone but the tank. When these guys are both around 30% push them quickly and cast DoT spells on both of them. Terrastra and Arion will replace them soon after. 

Phase 2 revolves around managing the two charge-up abilities that Terrastra and Arion have. Arion will cast Thundershock and Terrastra will cast Quake. These casts are on a long timer and rotate. The raid must have the grounded effect from the Gravity Well when Thundershock is cast and must be levitated by the tornado when Quake is cast. Aside from that the most vital part of this phase is to react quickly to players that are afflicted with Lightning Rod. Lightning Rod can and will wipe your raid in an instant if it's not managed properly. Have players with the effect move out of the raid quickly, and all players near them must react and move out of the way. Since you're going to be spending so much time running around trying to get grounded or levitated and managing Lightning Rods, boss DPS will be a bit chaotic. Arion and Terrastra have much less hit points than Feludius and Ignacious, so don't worry too much if this phase takes a while. Focus on executing it properly. As in phase 1 the raid leadership needs to monitor the hit points of each boss and insure that they are both pushed to 25% health at the same time. Once that happens everyone will be stunned and the Elementium Monstrosity will spawn. 

Phase 3 is controlled chaos. The monstrosity deals extremely high damage and must be kept in motion nearly all the time so that the pools of ice on the ground don't grow. Melee shouldn't even really bother trying to avoid the pools and should focus on maximizing their uptime on the boss when possible.  

A good strategy for this fight is to move the boss in a spiral pattern around the room either beginning in the center of the room or on the outside so that the ranged DPS and healers don't have to move around too much. They're going to have enough on their hands between trying to deal damage and spreading out so they don't link Electric Instability. Healers are going to want to monitor targets afflicted with Gravity Crush because they're going to take extreme damage. This ability is the major cause of random deaths when Electric Instability isn't an issue.  

Save bloodlust, DPS cooldowns, and potions for this phase. Use whatever you can to mitigate damage. Don't stand in the little flares of fire on the ground and heal and DPS your heart out. This phase is a race against time and is tuned fairly tightly for most players. If you did a good job of making sure that you pushed phases 1 and 2 at 25% on the dot then this phase will be difficult but doable since the monstrosity will begin with far less hit points. 

Good luck and good hunting. Cho'gall is next!

Video