The Infernal One (real name Soa) is the final boss encounter in the Eternity Vault operation.
8-man Normal Operation:
Soa, The Infernal One, is a 3-stage boss encounter.
First Stage - 100% HP - 75% HP
Soa will have a yellow shield around him at the beginning of the fight. He can not be damaged during this time. This lasts about 8 seconds after starting the encounter. This phase is fairly simple, just dps him down, ranged dps and healers to watch out for the growing green circles on the floor that come from the obelisks on the edges of the room.
Once Soa reaches 75%, a blue shield will surround him. Everyone needs to run to the outer ring as the middle area will crumble and fall after a short time. It is recommended that everyone runs to the west side of the room.
The raid must now jump down onto several platforms in order to reach the lower level. Destroy the obelisks on each platform on the way down. Be sure to keep each player's HP capped off so that a fall will not kill them. You will need to wait at times for new platforms to fall down, these are good times to drop aoe heals. Once you reach the ground floor, the boss won't come back out immediately, so this is another good time to cap everyone's HP before the second stage starts.
Second Stage - 75% HP - 35% HP
Mind Trap - Throws 1 random player into an obelisk. DPS needs to take these down immediately in order to pull the player back out. Players inside the mind trap will have a normal npc to deal with, but it has no effect on the fight. The only way to get out is to have the mind trap destroyed.
Ball Lightning - Spawns a lightning ball on a random obelisk around the room. It will target a random player and slowly path towards him/her. The raid will be warned as to which player it has targeted (each ball will stay on the same target). The ball will last a short time, it can be easily outrun, just be sure not to drag it through other people. It will damage anyone it passes by.
Force Throw - Soa will throw one random player into the air. They will hit several walls around the room before being slammed down on the ground next to Soa. The player will take damage each time they hit something.
The priority in this phase is to take out the mind traps as they come up. Simply dps him down to about 37-40%. You may need to hold off dps at this point to make sure a player is not in the air from Soa's Force Throw ability. The floor will fall again at 35% so this kill the player when they come down. Once Soa reaches 35% he will throw the blue shield up again and everyone will need to get to the edge of the room again. If a mind trap is still up at this point, it will despawn and the player will be released.
Again, players will need to jump down the platforms to get to the ground level. Taking out obelisks and healing along the way as before, nothing new in this part.
Soa has no new abilities here, but his blue shield will be up permanently (he can't be damaged when it is up). Soa will no longer use Force Throw here, but will continue to use Mind Trap and Ball Lightning.
If you look at the edges of the room, there are larger obelisks with an orange glow in the middle. Soa will pull one up and move it across the room and drop it in a random location. The tank will have to maneuver the boss under the falling pillar. It will do a decent amount of damage to the tank so be sure to watch his/her HP.
Once the pillar falls, Soa will be stunned and the shield will drop. This is the only time to put any dps on him, so it will be number one priority even over the mind traps. If the raid doesn't do enough damage or you miss too many of the pillar drops, you will hit an enrage timer. So definitely be sure to get him into position every time the pillar drops, and pop cooldowns when Soa is stunned.
A good tip for the tank is to position Soa in the middle of the room after each pillar drop so that he/she can easily get to the next. Bear in mind that the pillar will take some time to move into its position so be sure to adjust camera around to see exactly where it is coming down.