This guide provides tips and strategies for the fourth strike mission and how to defeat the Boneskinner in the Sanctum Arena of Bjora Marches. The high amount of incoming damage in this mission promotes bringing additional healers, but otherwise it is simple enough to not require a specific composition. However, if your group is struggling, the guidelines in Introduction to Raiding will apply here as well. Check out the glossary page if you're not familiar with a term used in this guide and make sure to run an optimal build from our list of recommended builds for this encounter.
Contents
- 1 Introduction
- 2 Strategy
- 2.1 Phase 1 (100%)
- 2.2 Phase 2 (90%)
- 2.3 Phase 3 (75%)
Introduction
The Boneskinner will spawn when the first player approaches the arena, and the encounter begins.Throughout the fight, players will receive a small amount of damage every three seconds from . The outside of the arena will be covered by a dangerous field that inflicts Unrelenting Pain, causing a player to take 20% of their maximum health as damage every second.
Strategy
Phase 1 (100%)
At the start of the encounter, there will be six lit torches at the edge of the arena, and throughout the fight these torches will be extinguished. For every unlit torch, the Boneskinner will gain a stack of – a pulsing effect surrounding the Boneskinner that increases in area and damage for each stack. A player may relight a torch by interacting with it. This is made more complicated by one of the Boneskinner’s basic attacks – Cascade – a series of rectangular AoEs that expand quickly out from the Boneskinner and deal heavy damage. This attack will not hit players close to the boss, but it can be very dangerous to players moving to relight torches. When not using other attacks, the Boneskinner will alternate between Cascade and Grasp.
Grasp
The Boneskinner raises its right claw, creating a small AoE under every player that fills will color. After a second and a half, each AoE will inflict moderate damage, 
Torment, and 
Weakness. At each location, a small field of grasping claws will be created that continues to pulse damage and Weakness every second for 30 seconds.
The long duration of the Grasp fields means that safe areas can become quite restricted if players are too spread out. A common tactic, therefore, is to stack tightly next to the boss (keeping the squad safe from Cascade) and rotate their position with each use of Grasp. While an individual instance of Grasp is not particularly dangerous, when 10 are stacked on top of each other they can instantly down a player and will likely kill them if they are not revived immediately. Skills and traits that can teleport downed players, such as 
"Search and Rescue!" or Transfusion, can be especially useful.
Death Wind
As the encounter starts, the Boneskinner targets a random lit torch with a narrow conal attack and spews forth a cloud that deals heavy damage, applies Torment, and launches players. The torch will be extinguished if it is lit. If there are no lit torches, the Boneskinner will target a random player. This attack repeats approximately every 15-20 seconds.
While the damage from is manageable, it can be very dangerous if the launch prevents a player from moving out of Grasp. As will regularly extinguish torches, will become increasingly more powerful. To counteract this, a player may move to the torch that has just been extinguished and relight it. Ideally, the player would be a support, as they will be more able to move off the group temporarily. It might be wise to wait until Cascade has just been used, to provide the time to reach the torch and return without risking being hit by the next Cascade, though the player should be aware that other mechanics may interrupt the Grasp-Cascade pattern. Assuming players are rotating around the Boneskinner to avoid Grasp, it is recommended they not stack directly between the Boneskinner and a lit torch to avoid .
Phase 2 (90%)
Shortly after the Boneskinner reaches 90% health it will rear up on its hind legs, gain a defiance bar (strength: 4000), and summon between four and six wisps nearby. Players with the Essence of Valor mastery will be given a Special Action Skill that provides some CC and damage. Breaking the defiance bar will 
Stun the Boneskinner and apply 
Exposed for eight seconds, but will not prevent the wisps from being summoned. The wisps will move to torches and attempt to extinguish them, and otherwise will attack players from range. Their attacks are not very dangerous, but if they are not dealt with the number of wisps may become overwhelming, so it is efficient to pull the wisps towards the group to cleave them down. Alternatively, as their attacks are projectiles then projectile defense is useful in mitigating the damage.
The Boneskinner will Summon Wisps approximately every 30-40 seconds, though there may be longer delays if the Boneskinner is performing other attacks.
On the first instance of this attack, all valid players should be given the special action skill. However, after this point, it appears and disappears quite randomly – possibly depending on whether there are still surviving wisps. It is unknown if this is intentional or not. As such, it can be very difficult to break any defiance bar other than the first, and players should be wary of using the special action skill as it prevents movement for a couple of seconds which can be dangerous if Grasp is about to spawn.
Phase 3 (75%)
Douse in Darkness
Shortly after reaching 75% health, the Boneskinner will leap up into the air and pull players towards the center of the arena. All the torches will be extinguished and a red AoE spreads out from the middle. As it reaches the edge of the arena, the Boneskinner will crash back down, dealing very high damage to every player. This attack will usually repeat at 50% and 25% health, though it will occasionally be canceled by other attacks.
Not only does deal a lot of damage, will immediately reach maximum stacks. It is therefore important that must be evaded or blocked. If the squad is attempting to keep torches lit, then it may be recommended that 6 players move out before the attack and stand behind the torches as this will prevent the players from being pulled into the middle. They can then be immediately relit (you can still interact with the torch while being pulled). Speed is important here as with maximum stacks the will be able to hit the entire arena. Following , the Boneskinner will use Grasp and (in either order) followed by:
Charge → Crushing Cruelty
The Boneskinner aims at a random torch and charges forward, destroying it. Any players in the path will take extreme damage. Following this, the Boneskinner leaps back to the center of the arena, dealing extreme damage to any players hit. The Boneskinner can charge at torches that it has already destroyed.
As with , players can stay safe from Charge by ensuring that they are not positioned between the boss and a torch. Crushing Cruelty’s AoE is small enough that it can also be avoided by staying out of the center of the arena.
At each 25% health interval the Boneskinner will attempt to use → Charge + Crushing Cruelty → Summon Wisps → Charge + Crushing Cruelty (with basic attacks in between each major mechanic). However, it will prioritize other mechanics over Charge + Crushing Cruelty so it is common for this attack to be skipped.
Because of Charge and leading to the unavoidable snuffing or outright destruction of torches, this encounter has a high healing requirement. And because squads will be taking a lot of healing anyway, it is popular to simply ignore the torches altogether in favor of stacking tightly, out-healing the , and simply rotating a small distance around the Boneskinner every time it uses Grasp.
