Before starting the fight apply a dose of smelling salts and drink a dose of liquid adrenaline if necessary. To begin the fight, a party member must speak to Osmumten.
Phase 1 - Obelisk
Spoiler
During the first phase of the battle, the obelisk will begin to emit orbs that transfer energy to the Wardens. Players can block these orbs by standing on either side of the energy troughs. This will significantly reduce, although not prevent, the Wardens' energy gain, however each orb absorbed will cause the player to take 3 damage. It is recommended to block one side of the energy troughs to desynchronise the Wardens' charged attacks, as it is much harder to avoid them if they are launched simultaneously. Players may also choose which Warden to fight in the second phase by selectively blocking the flow of energy to the Warden that they would rather avoid (in osrs wiki).
When a Warden is charged up, it will discharge one of two types of attacks:
Charged Shot - Slow-moving balls of energy will be shot towards players for unavoidable damage.In case of a large ball of energy, stand next to or on top of each other to disperse damage. Otherwise, stand apart from other players to minimize the amount of damage.
UFOs - Small floating pyramids will spread throughout the area and discharge damaging lights. Blocking the energy paths can cause the timings between each to be offset, therefore avoiding damage.
The Wardens will alternate between UFOs and Charged Shot respectively until the phase ends. Once the obelisk's health hits zero, the Warden whose energy gain was disrupted the most will be destroyed, but the other will activate and engage players in the fight (Phase 2).
Phase 2 - Warden
Spoiler
Regardless of which Warden powers up, the second phase of the fight is nearly identical. The Warden will always have protection prayers active against two attack styles, with Protect from Melee being always active; however Tumeken's Warden will always initially pray against magic, while Elidinis' will initially pray against ranged (in osrs wiki).
While the player is fighting the Warden, the obelisk will also discharge a series of attacks:
Converging Beam - The obelisk will shoot out two beams reaching either the north and south or the west and east end of the arena. Each beam will spread out and converge towards the obelisk. Players may avoid the damage from the incoming beams by running over them with proper timing. Red lightning will surround the obelisk as a warning indicator for the attack.
Windmill Beam - The obelisk will periodically shoot out beams clockwise in four directions like a windmill. The floor will briefly glow before the beam is discharged, giving players some time to move away from it. Orange lightning will surround the obelisk as a warning indicator for the attack.
Lightning Skull - The obelisk will launch several red skulls and discharge lightning outward in a 7x7 area from where the skull landed. Yellow lightning will surround the obelisk as a warning indicator for the attack.
Once the Warden's core is ejected, players must damage it as it essentially acts as the Warden's "true" health. Damage dealt to the core deals five times the damage towards the Warden, so a hit of 55 would deal 275 damage (in osrs wiki). The dragon dagger is a solid weapon against the core as each special only costs 25% (12.5% with liquid adrenaline).
After some time, the Warden will reclaim its core and change its overhead prayers, with Tumeken's Warden now praying against ranged instead of magic, and Elidinis' now praying against magic instead of ranged. They will always alternate between this and their initial prayers each time the core is exposed until the phase ends. The core will be exposed for a longer time each time the Warden is disabled.
Once the Warden's core is destroyed, its body will collapse. However, it will use the last of its power to restore the Warden that was destroyed at the end of the first phase. The obelisk will grow unstable and explode, and the room becomes warped in a void, beginning the final phase of the fight (Phase 3).
Phase 3
Spoiler
The restored Warden will not use any protection prayers or perform any combat style attacks. Rather, it will raise/slam the ground as its primary means of attack.
The Warden will always raise the floors to its right first, then its left, and lastly slam the ground in both directions. For the Warden's side attacks, players must stand at least one tile left/right from the center opposite of where the Warden is facing. When the Warden slams in both directions, players must stay in the center tiles in front of its face (in osrs wiki).
Upon reaching 80%, 60%, 40%, and 20% of its health, the Warden will stop slamming the ground and become invulnerable. It will then launch energy siphons onto the arena, which must be disabled by using a melee weapon. Successfully disabling all of the siphons will inflict massive damage back to the Warden. The Warden will reset its slam rotation to target the right side first if the Insanity invocation is not active; if it is, then the Warden will resume the pattern as before the energy siphons spawned.
At the second and third thresholds, phantoms of the bosses from earlier in the raid will appear and assist the Warden against the player. The first phantom will spawn east; if Elidinis' Warden is being fought, this will be Akkha's Phantom, with the other phantom being Kephri's. If Tumeken's Warden is being fought, this will be Zebak's and Ba-Ba's Phantom respectively (in osrs wiki).
When the Warden reaches ~5% of its health, it will heal back to 20% of its max health and become enraged. It will no longer slam the arena, but will instead begin to emit unstable bolts of energy across all walkable tiles in the arena that deal moderate damage to any player standing on a targeted tile.
As the fight progresses, the dark phantom behind the Warden will begin to tear the tiles from the floor, limiting the amount of space players can move around in, up to the first row next to the Warden. Standing on where a tile would be ripped will force the player into the next row and take damage in the process. Keeping ambrosia for this purpose will help minimise distractions.