Shattered Observatory (CM)
To start the Challenge Mode (CM), a player who has completed all Shattered Observatory achievements must interact with the Challenge Mote to spawn the Harbinger of Woe, who will ask the party whether they want to turn Challenge Mode on. Once on, players must jump down the rocks to the platform and interact with an orb to start the first boss.
NOTE: This guide is written under the impression that players already know the Normal version of Shattered Observatory.
Skorvald the Shattered
Skorvald the Shattered will have all of his normal mechanics but they are faster, larger, and deal heavier damage. When Skorvald reaches 66% and 33% health, players must kill 4 Anomalies within the time limit. Skorvald will charge an attack that will wipe the party if the anomalies are not killed quickly enough.
At the start of the fight, Skorvald will appear with a Defiance Bar.
Skorvald will charge a laser that shoots across the platform, ultimately one-shotting players. During this mechanic, Skorvald will also have an eye above his head. Players should face away from the boss to avoid its 
Fear
After 66%, Skorvald the Shattered will fixate and teleport around the platform, performing an attack similar to 
Surge of the Mists
Skorvald the Shattered targets a player with a bomb icon above their head. A few seconds after this, Skorvald will teleport to the player and deal damage. Simply time your 
Dodge
Skorvald the Shattered will become enraged a few seconds after the 33% phase, growing in size and hitbox. He will begin to spin around the platform starting from the direction he is facing with aggressive knockback strikes for about 15 seconds. 
Stability
Artsariiv
In the Challenge Mode version of Viirastra, there is a noticeable increase in AoEs.
At the start of the fight and after every phase, Artsariiv will charge a triple laser with the eye mechanic. Look away from her to avoid getting afflicted by Fear
Side Slam: Artsariiv jumps into the air and slams the ground, knocking all players that get hit. Either dodge the AoE or use Stability
Corporeal Reassignment returns in the Challenge Mode of Artsariiv, but a Temporal Anomaly will spawn in the middle of the platform. Killing the Anomaly will spawn the protective dome.
During her first Split Phase, she splits into 5 clones – one in each corner and one in the middle. In the second Split Phase, she splits into 9 clones, adding 4 clones between the corner ones.
The Ball Mechanic is mostly the same, except for the fact when a bounce is missed, not only will Artsariiv go to another corner, but all players will also get downed from the ball’s explosion.
TIP: After each Phase, all players get revived, so do not worry too much about dying during a phase.
Arkk
In the Challenge Mode variant of Arkk, Arkk will instantly appear in the middle of the platform once the fight has begun, and there will be no reactor mechanic during this phase. Instead, Arkk will start with the eye mechanic.
At 80%, 50%, and 30% the reactor mechanic will appear. Be sure to be ready to finish it quickly, so your party does not wipe.
Greens: like many other End-Game content in Guild Wars 2, Arkk will spawn a Green Mechanic. This one is a lot simpler – it will be stuck on a player and only requires 1 other player to stand in it to avoid damaging your party.
Corporeal Reassignment returns once again, and as in Arkk’s Normal Mode, its spawn is random. However, in CM it spawns a Temporal Anomaly in a random location on the platform which has to be killed to spawn the protective dome.
At 70% Arkk will leave the fight and you’ll be introduced to an Elite version of the Legendary Archdiviner and some additional mobs. Kill the Archdiviner to bring Arkk back to the fight. During this phase, Arkk may appear on the West side of the platform with the Eye mechanic, remember to have your character look away from the Arkk to avoid getting Fear
In the last 40%, platforms will begin to disappear. If a player falls through one, they will be teleported extremely high in the air. You will need to use 
Nova Launch
