Introduction
The Cathedral of Light Capstone Dungeon is the first big challenge to tackle once you have completed the Campaign. It is a level 50 (the mobs are fixed at level 50 and do not scale down if you are lower level) Dungeon located in Kyovashad, within the Fractured Peaks, and is only available at the World Tier 2 difficulty. The enemies within this Dungeon hit quite hard, most dealing Lightning Damage. Besides these mobs, Cathedral of Light has two boss fights; The High Council and The Curator. Once cleared, the World Tier 3 difficulty will become available.
It is highly recommended you bring some form of Lightning Resistance to this dungeon. This can be supported by using an Elixir providing Lightning Resistance. Outside of this, having a full understanding of the boss fights will help avoid frustration and your time being wasted.
Video Guide
The High Council
The High Council is the first boss fight of the dungeon. It consists of the Lord Commander and his Captains. The council-style fight is very straightforward, but can become very hectic if executed incorrectly!
We recommend the following kill order for this fight: Sacred Physician > Grand Inquisitor > Devoted Champion > Lord Commander.
The Lord Commander is quite slow, both in his movement and attacks. All you have to do is stay away from him to avoid his damage. The recommended strategy is to kill the Captains while avoiding him.
The first Captain, and the most important one to kill, is the Sacred Physician. This enemy caster does very little damage compared to the others, but will resurrect his fallen comrades should you kill one of them first.
Next up is the second Captain, the Grand Inquisitor. She will teleport to you and deal Lightning Damage. This is the hardest ability of the fight to dodge, thus making this the ability that you will take the most damage from. Kill her next.
The final Captain is the Devoted Champion, who will run after you with a spear and try to hit you throughout the fight. Simply avoid his attacks while focusing on the previous two Captains and finish him off after the Grand Inquisitor.
Note that once the Sacred Physician has been killed, slain Captains will turn into ghosts instead of lying on the ground. These ghosts are still able to use their abilities, dealing reduced damage to the player, however they cannot be resurrected. Try to keep your cool with this messy fight.
The Curator
The Curator is the final boss of the Capstone dungeon, and despite having well-telegraphed abilities, he hits hard, and we do mean it. During the fight, you will be bombarded with Bone Spirits that track your position that can become a problem if you are followed by several of them at the same time. Run circles until they expire.
The first major ability you have to contend with is a cone-shaped slash, which creates three lines of damage fanning out in front of The Curator. There is a small window of time during which you can reposition yourself to dodge these.
As the fight progresses, The Curator will periodically summon generic adds to assist him during the fight. It is strongly recommended to kill the adds as soon as you see them, taking special care to kill the Ballista-type Skeletons first, as they deal high damage with their long-range snipe. You can sidestep this attack, but the long range can make them unpredictable.
Otherwise, you should try and stay out of the ever-present damage puddles that spawn on the ground. For the most part, the fight is a classic tank and spank.
As the fight progresses however, The Curator will begin to use the aforementioned cone slash ability multiple times in quick succession, coupled with casting Bone Walls randomly around the room. When this happens, it is much harder to manually dodge the slashes, so having access to a defensive cooldown, such as 
Blood Mist or 
Deep Freeze, is particularly useful to survive this.
About 20 seconds after creating the Bone Walls, The Curator will also detonate any remaining ones, which deals high damage around each of them. It is not advised to try to kill the Walls, but before the detonation happens, you should move away from them, so as not to take any damage. Having some form of mobility skill is very helpful for this reason.
