Starting area and the tunnel

Go to Rox and Braham, wait for the mobs to spawn, kill them. After killing them, proceed into the tunnel, there are 5 caves in the tunnel, each having a group of mob in it, after killing the mobs, destroy the Boulder that becomes damageable (a red gear indicates it’s place). After killing all 5 group of mobs and destroying all 5 Boulders on the red gears you wait for the Drill to make it’s way out of the tunnel (which should already be done).

On your way to the Boss

Exit the tunnel and kill the group of mobs coming towards you. Then proceed to the Steam Walls. The first Steam Wall is impassable, wait until it lowers before moving on. Each Steam Wall will knock you back and damage you. After the first wall, you can now pass the Steam Walls by walking backwards through them or using Stability. Do not pass through them with low HP, as this can down you or kill you. Once through the walls, make your way to the weapon testing arena.

Weapon Testing Arena

After entering the arena (and at each new phase), 2 Champions spawn, which your party needs to separate and kill. Not separating them will cause them to reflect damage back to the attacker via a unique buff called Sentinel Retribution .

At the same time, you will survive a series of weapons tests.

The weapon test types include:

Fireball Barrage

You have to avoid, block or reflect the Fire Barrage falling on you, place reflect (Guardian with Wall of Reflection ) or absorb (Revenant Legendary Centaur Stance with Protective Solace ) in the middle of the AoE to absorb the projectile. The projectile leaves behind an AoE that applies Burning. After surviving the test you can damage 25% of the Thermal Core.

Fire Tornadoes

You have to dodge, avoid, or negate the Fire Tornadoes coming towards you. The Tornadoes damage you, apply Burning and knockback. Stability is useful here to avoid knockback. Please note that since the rework, the Fire Tornadoes go through the Thermal Core. After surviving the test you can damage 25% of the Thermal Core.

Shockwaves

You have to dodge, block or jump over the shockwaves coming towards you. The shockwaves apply Knockdown. Stability is useful here to avoid being knocked down, but you will still take damage. After surviving the test you can damage 25% of the Thermal Core.

25% Phase

At 25% the same weapon’s test will be active, though now all 3 weapon test types will happen at once. Simply damage the core as fast as possible to move on to the final boss fight.