WoW Ulduar Raid Boss Guide - Thorim
Thorim is one of the longer and more difficult encounters in Ulduar, technically being the 11th boss. Only with a good group balance and players that are very aware of what is going on will you be able to defeat him. Get the full Thorim strategy here.
Thorim is one of the watchers, located around the Ring of Observation in inner Ulduar. You can do the Watchers in any order, but Thorim is technically considered to be the 11th boss. Anyone who has completed all of the Sons of Hodir quest lines will remember that Thorim was once the guardian of Ulduar, and of the pact of the races of Frost. When Yogg-Saron corrupted Loken, Loken betrayed Thorim by murdering his wife, Sif. Loken led Thorim to believe she was killed by the leader of the Frost Giants, and he warred against them. Afterwards, he spend the rest of the time in a stupor upon his throne in the Temple of Storms. In the Hodir quest line you rouse him from his dazed state, and he reforges his relationship with the Frost Giants. He also realizes that Loken is the real enemy, and goes to engage him. It is all a ruse, however, and Loken, strengthened by his proximity to Yogg-Saron, defeats Thorim and takes him into Ulduar, where he is brain washed into believing that Sif is still alive, and your raid is the enemy.
The Thorim encounter is separated into three distinct phases. The first phase is a very simple and easy clear of the mobs inside of Thorim's arena. He stands on a platform above. Have your tanks lead the charge in and pick up all of the mobs. Kill the Acolyte healer first, then the rest. Make sure that the Jormungar (giant worm) is tanked facing away from the group because of a conical AoE poison attack.
Once all of the initial mobs are dead, the lever for the gate in front of the tunnel leading to Thorim will become usable. At this point, your raid will need to split up into two groups.
Phase Two - Arena
One of the simplest ways to divide up the groups is to send half of the healers and tanks, and all of the casters up the Tunnel and leave the other half of the tanks and healers, and all of the melee DPS in the Arena. You want to make sure the groups are roughly even, however, so balance as you need to. Your Tunnel group needs to be able to move quickly, but you cannot do this at the cost of letting your Arena group be overrun.
The easiest way to position the arena group is to have the healers against the back wall, in the smoke, with the tanks and melee DPS a couple of yards closer to the center of the room. Little movement is required, accept to get away from the pillars when they do their lightening arc. There are several types of mobs that will drop into the Arena.
The most important add to take down first is the Dark Rune Evokers, who can cast a very powerful heal. If the heal lands, it will need to be purged/dispelled. The second add on the priority list is the Dark Rune Champions, who do very heavy melee DPS including a Mortal Strike and a Whirlwind. If these are not picked up immediately they can easily kill off your healers. There are two other types of adds, including the Dark Rune Commoners which can be safely tanked then ignored until everything else is dead.
While you're dealing with all of the adds in the Arena, Thorim will also be attacking. The main attack is when he throws his Stormhammer at a random target, which stuns them and also does a silence in the area around them. Other than that, the only other attack is through charging the pillars, which do a lightening arc as discussed above.
Phase Two - Tunnel
While your Arena group is fighting adds, the Tunnel group will be working their way upwards. The tunnel team will encounter a few packs of trash mobs along with two mini-bosses. As you are clearing trash to the first mini-boss, you'll notice that he is always charging up a fire attack in one of his hands. The group needs to be aware of which side he is charging the attack on, call it out, and move to the opposite side to avoid it. He will unleash several of these attacks before the group reaches him, so everyone needs to be on their toes.
The first mini-boss needs to be tanked facing away from the group to avoid the frontal AoE cone and his Smash ability. He will occasionally charge someone, and can often immediately cast Smash before he is repositioned, so the whole group needs to be sure to move behind him after a charge.
After the first mini-boss is dead, you will continue to be attacked by waves of trash groups until you have pulled the second mini-boss. This means that you must kill the trash quickly and move ahead or you will hit the five minute timer and fail.
The second mini-boss has a small AoE ability that will hit and knock back anyone in melee range. He also has another ability called Rune Detonation, where he roots a random player and after four seconds causes them to explode, dealing significant damage to the group. The group needs to make sure to continually move away from whichever player has Rune Detonation, as he will use it multiple times. After defeating the second mini-boss, move forward to engage Thorim while avoiding the large circles on the ground. If you run through them, they will trap you for a few seconds.
Once your tunnel group reaches Thorim, they need to jump back down into the Arena to help them clear up any remaining adds. Thorim will follow suit, but he cetainly won't be helping!
The tunnel tank should pick up Thorim right away, while the rest of the raid cleans up the Arena adds. Once they're all dead, DPS can start in on Thorim.
Thorim should be tanked in the center of the room. It is basically a pure DPS burn from here on out, but there are a few things to be aware of. Thorim will continue to charge the pillars in the room, but instead of them doing a simple lightening arc, orbs of lightening from Thorim to the pilar will precede a massive lightening cone explosion that must be avoided. When you say the little orbs, move away allowing roughly a 120° angle of clear space around the pillar.
In addition to the pillar attack, Thorim will also cast chain lightening on a random player. Because of this, everyone needs to be very spread out around the room so as not to chain the lightening amongst the raid, particularly to the melee where it could have detrimental effects.
Lastly, Thorim will use an ability on the tank called Unbalancing Strike, which reduces the tanks Defense skill making him critable. As soon as this strike lands, the off tank must taunt him off. The tanks need to continue to swap, so that the one afflicted by Unbalancing Strike is never tanking.
Stay sharp, and you will easily defeat Thorim!