The Bastion of Twilight - The Twilight Ascendant Council

Here is a Video guide of The Twilight Ascendant Council (25 man). It explains all we need to know about this fight on normal mode. Couldn`t find a good 10 man version, but its all the same abilities.

https://www.youtube.com/watch?v=dQSkOh_6ksg

Hope it can be of any use

Regards Amourus

Healing

Taken from http://wow.joystiq.com/2011/03/28/spiritual-guidance-priest-healing-ascendant-council/

Phase 1 and 2
In the first two phases, there isn't any best way to heal the encounter because the damage is both random and subject to the skill of your raid. To counter that, it's best to identify the slow learners in your raid and try to compensate for their mistakes.
Cooldowns of any sort can be used liberally as long as they're available again for phase 3. If you're healing the tank, you should be able to work in low-cost spells in between your other single-target spells. Regardless of your role, try to conserve as much mana as you can for phase 3 by not being wasteful.

Heart of Ice and Burning Blood
Though there isn't too much finesse required to heal through the first two phases, there is one aspect of phase 1 that you'll want to learn properly: dispelling the two nearly identical debuffs, Heart of Ice and Burning Blood.

To handle this, think back to how you handled Necrotic Plague on the Lich King encounter in Icecrown Citadel; don't dispel the debuff until the player is in the correct location.

Phase 3
Once all the elemental ascendants combine into Captai-- err, rather the Elementium Monstrosity, the real fun of the fight begins. This phase is a DPS race, and your job as a healer is to try and keep up

Melee in particular will need a little bit of extra attention due to Liquid Ice. Try to find a spot in the room where you can either be at the center of the fray and be in range of everyone or on the outskirts where you'll be free to move ahead of the kite path of the boss.

You probably won't need healing cooldowns on your tanks, so save them for your best DPS on those 1 or 2% attempts.

I noticed that the majority of the damage was coming from two aspects of phase 1. When a hydrolance got through to a player and during the Aegis of Flame. Aegis of flame being the attack where he gains a shield and starts erupting.

With the Aegis people seemed to die a lot here. I think a healing order is essential for this part of the fight because if you have two healers healing the same player then you are not only wasting mana, you are also allowing other players to get double the damage from the eruption. If for example I see a Paladin who gets 1 tick of damage and I and another healer go to heal him at the same time, then two more players get a tick and two more healers only heal one of those players then someone is going to die. This can only be avoided by setting up a healing order to avoid duplicate heals, it is also very important for mana conservation since overhealing is 100% a mana loss.

Two of the important factors in phase two are the special attacks you need the correct buff for and also the Lightning Rod.

Lightning Rod is a debuff placed on a player. That player will get a yellow arrow on top of their head and will damage everyone around them for a serious amount of damage (capable of wiping the raid) if this happens run out of the raid as fast as you can until it goes away.

If you have to choose between getting your debuff for the special attack or running out of the raid because of lightning rod then choose to run out. It is possible to survive the special, cept the healers will hate you, but lightning rod can and will kill people almost all the time.

Another thing I noticed was that we were not getting the bosses down equally. I'm not certain if this was to nuke the fire one and learn more of the fight but when it comes to phase 3 if we don't do this then the phase 3 monstrosity will have waaaaaaaay too much health. If we kill them equally the monstrosity will be around the 15% mark and will be easier to nuke down.

Also in phase 3 the center of the room is the start position. The pools of water act like defile except when the boss stands in them they grow, not players. The room will fill up like Putricide while you nuke the monstrosity.

It is a dps race.

There will also be chain lightning comming from the boss to a random target so dont hug up in Phase 3. And ofc heal the shitt out of ppl that get grabbed as they will aslo take fall dmg when he relese them

Phase 1 things we might miss

hydrolance - "MUST be interrupted"
Aegis - "To counter this, you need to have all your DPS switch to Ignacious as he is casting the shield - or even better, 3-5 seconds before he does it, - burn through it ASAP, and then interrupt Rising Flames. If done right, you shouldn't get more than 2-3 ticks."
Glaciate - "To counter it, run away from him at the beginning of the cast (tank included), and get rid of your Waterlogged quickly. Also, make sure to interrupt the Hydrolance that tends to follow."

"With all DPS switching to burn down Ignacius’ shield, it is most likely that Feludius’ HP will be higher. Wait until both health pools are equalized before pushing one to 25%."