CO: Challenge mode

In CM, the boss periodically gains ten stacks of a damage-reduction buff. Collect the white orbs shown around the arena and hit the boss with the special action skill to remove it. (Each orb removes five stacks, so two players should keep collecting orbs and clearing the buff.)

Healers or boon DPS players usually handle the white orbs to limit lost damage.

If you receive the green target, move behind your allies. At least five players must stand in front of the targeted player to complete the mechanic. (With fewer than five, the target dies.)

Players targeted by the red ground effects now receive five areas. Once all five appear, they follow you as shown. Remember this timing and keep moving when targeted.

The boss's red attacks apply stacks of the debuff shown here. At ten stacks, you turn hostile to your allies. This also happens in normal mode, but the debuff becomes permanent in CM.

(Watch out for the boss's red attacks and red ground effects.)

If someone turns hostile, use crowd control to free them. This also resets their stacks.

In CM, the boss gains a dash-and-slash attack. Players marked with numbers should spread out to handle it.

Players hit by the slash receive the debuff shown here. Another slash while the debuff is active kills you instantly.

(The slash hits an area, even though the image does not show its full reach. Leave plenty of space when positioning.)

CM adds a green ground area. Although the indicator shown says there are too many players inside, you can ignore it and stay stacked.

Red ground areas now appear around the arena during the bomb mechanic (orange circles) and the numbered slashes.

(Players with slashes can stand in front of the red circles. Players with bombs can each take a separate gap between the circles.)