As usual, the encounter is started by talking to the NPC. The Twins and four portals spawn: two portals near the Twins, and two on the opposite side (near the NPC and the door). If the whole raid stays close to the NPC, the Twins will not aggro. It's also safe to use the portals on the NPC side of the room. The four portals - two light, two dark - are the central element of the encounter. Using one of them gives the player either a light or a dark buff. This buff reduces damage against same-color targets by 50%, but increases the player's damage against opposite-color targets and makes the player immune to same-color damage.
To address this mechanic, the raid should be divided into two halves. Both halves should have one tank, a similar number of healers, and be able to deal similar DPS. One half of the DPS takes the light buff and sets up near Eydis Darkbane; the other half takes the dark buff and goes to Fjola Lightbane. Each tank takes the buff of the opposite color as the boss they will be fighting, as otherwise they will not be able to keep aggro. The Twins' melee damage is not modified by the tanks' colors so this is a non-issue. The Twins share a health pool and will die simultaneously without any special coordination on the raid's part.
Orbs
Once the encounter is started, light and dark orbs spawn from the walls at regular intervals and move randomly around the room. If they touch an opposite-color player, the player takes 7000 damage. To mitigate raid damage from these, healers should attune to the opposite color of the DPS group they are healing and act as soakers for orbs of their color. For example, a light-attuned healer should intercept light orbs headed for the group of dark-attuned DPS attacking Lightbane, but allow the dark orbs through. (Fire Resistance and Shadow Resistance Aura may also be helpful, as the light orbs do Fire damage and the dark orbs do Shadow.)
If the orbs touch a same-color buffed player, the player receives a stacking speed and damage buff called Powering Up. At 100 stacks, this will trigger Empowered Light or Empowered Darkness, which increases damage dealt to same-color targets by 100% for 20 sec. Thus both DPS and healers should actively seek out orbs of the same color as their essence to acquire this boost.
Special Abilities
The Twins share the same two main abilities: Vortex and Twin's Pact. If either Twin uses either of these abilities, the other half of the raid must swap their color buff, wait until the effect is over, and then switch back to their original color. The abilities are used in a random order, but the Twins will cycle through all four abilities - Light Vortex, Dark Vortex, Light Pact, and Dark Pact - before repeating one. This gives the raid some limited ability to predict which is coming next and preemptively swap colors if necessary.
Vortex
When one boss casts Vortex (8 sec. cast), each player must be sure to have the same-color buff as the boss who is casting or they will take a total of 30,000 damage. After the Vortex is finished, the affected players should switch back to their original color. This swapping is made simpler by tanking each Val'kyr next to a portal of the same color so that, for instance, light-attuned melee attacking Darkbane can quickly and easily attune dark to survive her Dark Vortex, then run to the light portal to reattune.
Twin's Pact
If either Lightbane or Darkbane casts Twin's Pact, that twin shields herself and begins a 15 second cast which heals the Twins for 20% of their maximum HP. In order to interrupt the cast, the shield must be removed by damage. All damage dealers should change to the appropriate color to bring down the shield. Once the shield is down, the cast must still be interrupted. In standard UI, if the enemy cast bar is turned on, the cast bar will be in metal frame indicating it is uninterruptable. The moment the shield is down the frame will disappear so it can be used as an visual clue. Deadly Boss Mods will also throw up a warning saying "Interrupt Now" when the shield is broken.
In addition, when Lightbane or Darkbane cast Twin's Pact, the other gains Power of the Twins for 15 seconds. The tank on the Twin not casting will take increased damage during this time, as each melee hit the Twin lands increases her attack speed until Power of the Twins fades.
Otherwise, the Twins deal insignificant tank and raid damage. Players just need to focus on the following list:
* If the other twin casts Twin's Pact, switch color to DPS her, then switch back after Twin's Pact is interrupted
* Switch color if your own boss casts Vortex, then switch back after the cast is over
* Try to catch orbs of your own color for the dps boost, while avoiding those of the opposite color
Focus-fire alternate strategy
Have the majority of the raid attune to one color and attack only one Twin. If, for example, the raid attunes light and attacks Darkbane, this trivializes Dark Shields and Light Vortexes, and the raid only really needs to worry about the other two abilities. To further simplify the encounter, raids who choose to focus damage on only one Twin often ignore shields on the other Twin and allow the 20% heal to go off. However, this is only viable if your raid has high enough DPS to compensate. Healers should still attune to the opposite color of their targets and act as orb soakers.
