Thorim is one of the boss encounters in Ulduar. In order to defeat Thorim, players must go through a gauntlet starting off with a Jormungar Behemoth and a rush of iron dwarves.

Abilities

Gauntlet Related

• Charge Orb: Charges a nearby orb with electricity. Orbs affected by this ability gain a periodic effect that fires a Lightning Shock every second, inflicting 2831 to 3169 Nature damage to a nearby enemy. Lightning Shock has a 35 yard range so it can be avoided by standing in the center of the room.
• Sheath of Lightning: Encases the caster in a sheath of pure electrical energy, reducing all damage taken by 99%.
• Stormhammer: Throws a stormhammer, dealing 2451 to 2551 damage to an enemy, knocking down and stunning the target for 2 sec, and causing a deafening thunderclap to all enemies nearby the target. He will only use this ability during the Gauntlet portion of the fight. After he leaps down from his perch, he will no longer use this ability.
• Summon Lightning Orb: Summons a supercharged ball of energy, laying waste to all in its path. This ability is used if either a) no one is in the room below where Thorim stands, or b) if five minutes pass and no one reaches Thorim.

Encounter

• Chain Lightning: Strikes an enemy with a blast of lightning that inflicts 3700 to 4300 Nature damage. The bolt will arc to additional nearby enemies, inflicting 50% more Nature damage to each successive target.
• Lightning Charge: Absorbs a torrent of electrical energy, inflicting 13875 to 16125 Nature damage to enemies in a cone between the caster and the power source, and gaining a stacking buff called "Lightning Charge" that increases Thorim's melee damage and attack speed by 15%, and Nature damage dealt by 10%. When he uses this ability, the "power source" used is one of the pillars with the orbs attached.
• Melee strike: deals ?? physical damage.
• Unbalancing Strike: Inflicts 200% weapon damage and leaves the target unbalanced, reducing their defense skill by 200 for 15 sec. Tanks need to taunt off of each other to counter this.

Adds

Initial Mobs

• Jormungar Behemoth

Gauntlet Mobs

• Ground slamming guy (not real name)
• Large storm giant guy (top of the stairs, not real name)

Entrance Room Mobs

• Health: 190,000.
• Abilities
  • Melee strike.
  • Aura of Celerity: 20% spell and melee haste to allies.
  • Rune Strike (melee strike + 1000 nature damage).

• Health: 162,000.
• Abilities:
  • Runic Lightning: 45 yd range, 1.5 sec cast; strikes an enemy with a blast of runic lightning, inflicting 7875 to 10125 Nature damage.
  • Runic Mending: 40 yd range, 2 sec cast; heals an ally for 18500 to 21500, then heals for an additional 6000 every 1 sec. for 15 sec.
  • Runic Shield: 30 yd range, 0.5 sec cast, 6 sec cooldown; surrounds the caster with a runic barrier, absorbing 120,000 magical damage and reducing all Physical damage taken by 50% (lasts 1 minute).

Strategy

At the start of the fight when you engage the Jormungar Behemoth and the other adds, Thorim will cast Sheath of Lightning on himself, making him almost entirely invulnerable to attacks. Have one tank turn the Jormungar away from the raid, and have the rest tank and AOE the adds, focusing primarily on the healers (the smallest one in front and the dark runed dwarf in the back).

After the initial mobs are down, the lever next to the gate on the left will become active. The raid should now split in half; one half should go down the hallway to reach Thorim, and the other half needs to stay and fight off adds and attacks by Thorim.

The Gauntlet

The gauntlet requires a minimum of a Tank, a DPS, and a Healer. It is best to have additional DPS, preferably as much as you can spare from the group killing adds, to quickly reach the end of the gauntlet where Thorim will engage the party. Speed is key at this point, because after five minutes he will wipe the raid. It is also important because everyone in the raid will be taking a lot of damage and healing becomes an issue during the encounter with Thorim.

Entrance Room

Those staying in the room will need to stack up in the middle to avoid the charged orbs around the sides. This will also make AOE healing to allies and AOE damage to enemies easier to dish out. Your priority here are the large runed Vrkyul who appear (the tall humanoids). But make sure to spread out when he targets someone with a stormhammer.

Boss Fight

Once the gauntlet group reaches Thorim he will jump down, he needs to be picked up by the MT immediately. About 15 seconds in he will do his first Unbalancing strike, when he does this, the OT needs to taunt immediately. When you see the little lightning balls coming from a column this means he is about to use lightning charge, and that side of the room in a 60 degree angle around the column wil be shocked for a very large amount of damage, one shotting players after the third one. Spread out around him to avoid chain lightning links as well.