Update on 4th boss Strat:
The boss is pretty similar to the Lair of the Demon Dragon in AV, where the boss is "chained" up. In order to release the boss, there are four mobs in each corner of the platform (channelling on an Imprisonment Crystal).
The boss buffs himself with Body Strengthen that gives him a Mdef/Pdef/PA buff which makes it reduces the damage he receives from Magic/Physical and also makes him hit harder.
As soon as you kill the 4 of the mobs (actually, once you actually pull the 4th mob, after like 5 - 10 seconds, the boss will aggro whoever pulled the last mob.)
Best way to do it:
Kill 3 mobs who are channelling the Imprisonment Crystals. (They don't hit hard btw.)
The tank pulls the 4th mob and starts fighting him. Everyone else in the party should be standing on the door of the boss room. Once the boss is aggro'ed, He will only kill the tank and reset.
In order to avoid getting locked out, you will notice that there is a "2nd" door for the boss room. Move to the left side of that door and move just infront of it. (Stick to the wall) to avoid getting locked out.
The best thing to do for this boss fight is to ensure you can burn as much as you can before he does his first attacks.
He casts the following spells:
Body Strengthen (Buffs himself.)
Annihilation Attack. (Gauteikriistain'na Cashtei will be said before he does this.)
Annihilation Beam. (Vaistain' Vaistain' Vaistain' will be said before he does this.)
Annihilation Attack will wipe the party if you refuse to do the strat.
Annihilation Beam is pretty much a laser that follow a specific player that hits for ~70k. (Dodge, Dodge Dodge! If you don't know how to run, you need to learn.)
What we do on Grimdal is since we do a lot of damage, we only follow the strat that protects us from Annihilation Attack.
Now to the Strat:
There are four Imprisonment Crystals in each corner of the room.
If you choose to follow the strat completely. Assign one person to each Crystal. (1 Tank, 1 healer, 4 DPS.), Tank the boss in the Middle of the Room.
When he says "Gauteikriistain'na Cashtei", all the 4 DPS should be ready to run to their assigned crystal and click on it. (ONLY ONCE) If you click on it twice, you will restart your cast.
Each Imprisonment Crystal has it's own coloured Crystal just behind the white sparkling light.
Yellow: 8k Blood DoT every (second?) for 10 seconds. - This protects you from Annihilation Attack. IF YOU MISS THIS, YOU DIE.
Blue: I think this one is the Pattack Debuff (Greatly reduces Pattack of the player and Removes Any Pattack Buffs on the boss.)
Red: I think this one is the Aggro Debuff (You get Aggro from the boss but can easily be regained by the tank, This one removes any Pdef buffs on the boss.)
Green: I think this one is the Mattack Debuff (Greatly reduces Mattack of the player and Removes Any Mattack Buffs on the boss.)
This strat isn't too difficult. You do not need to do the complete strat to avoid wipes.
Tl;dr Version.
1) 4 Mobs, Kill 3 with full party then Tank attacks 1 with the rest of the party at the door. Once the boss is "unlocked" swap and die at the door.
2) Burn as much as you can of the boss. (Assign one person to click on the Yellow coloured Imprisonment Crystal). After 20 seconds of burning, the boss will say "Gauteikriistain'na Cashtei", Assigned person clicks on the Yellow Crystal.
3) A couple seconds after you survive Annihilation Attack. He will say "Vaistain' Vaistain' Vaistain'", scatter from the boss and run away from the LASER BEAMS!
4) Rinse and Repeat until dead.
If you choose to do the full Strat, Assign 1 DPS to each crystal and as soon as he says "Gauteikriistain'na Cashtei", Let them click on their assigned crystal and continue burning the boss. Kite the Beam whenever possible.
You cannot immune his annihilation attack or beam. A bubble can reduce the damage of Annihilation Beam but it can still kill you if you stand in it.