The Guidance Node has led you to the Aetherochemical Research Facility on the Flagship in Azys Lla.
How to Unlock
The Aetherochemical Research Facility 4-player dungeon is unlocked by the level 60 Main Scenario Quest Heavensward.
Regula van Hydrus
Regula will sometimes cast Judgement on a random player, which stuns that player temporarily.
After a certain amount of damage, Regula summons a Magitek Turret I, which tethers to a player and shoots at them. Other players can pick up the tether by walking between the turret and the currently tethered player. The tethered player can turn the turret to face away from the rest of the party. While the turret is alive, Regula will target random players with Magitek Slug, a line attack. If the turret is not killed after a certain amount of time, it will self-destruct, damaging all players.
After a certain amount of damage, Regula summons both a Magitek Turret I and a Magitek Turret II. The Magitek Turret I behaves the same way as before. The Magitek Turret II will periodically target random players with Aetherochemical Grenado, a circle attack. Again, the turrets will self-destruct if not destroyed in time, damaging all players.
After the turrets are gone, Regula goes to the center and casts Magitek Spread. Get into the cone behind Regula to avoid getting hit.
At different times during the battle, Harmachis will use Weighing of the Heart to change form.
While in Anti-Cobra form, it casts Steel Scales, which gives it a Damage Up status that increases its damage output. It will also attack the player highest on the enmity list with Hood Swing, a high-damage attack.
When back in Sphinx form, it will attack the player highest on the enmity list with Chthonic Hush, a cone attack in front of it, which inflicts Poison. It also attacks players with Riddle of the Sphinx, a circle attack.
When Harmachis switches to Anti-Naga form, it sometimes casts Petrifaction, a gaze attack that petrifies players. Players need to turn their characters to face away from the boss to avoid being petrified. It will also cast Circle of Flames on multiple players at once. Stay apart from each other to avoid stacking the damage from this.
When Harmachis goes back to Sphinx form at this point, it may sometimes cast Ka, a cone attack.
When Harmachis switches to Anti-Machina mode, which looks like a four-armed robot, it will mark a random player and cast Inertia Stream, which inflicts Bind on the player. It will then hit the affected player with Ballistic Missile. Other players should stack together with the bound player to share the damage. It will also use Gaseous Bomb, a cone attack.
Lahabrea and Igeyorhm
Shadow Flare damages all players.
Fire Spheres will appear in the area. Stay away from them, because they will do circle attacks centered on themselves.
Igeyorhm casts Grip of Night, a wide cone attack. Get behind her or to the sides to avoid the attack.
Tethered Fire Spheres appear. When the enemy casts Esoteric Fusion, the spheres will move toward each other along the tether. They will do a large circle attack centered on the point where they collide, so move away from where the collisions will occur.
Circle of Ice creates ice spheres. Each sphere will perform a donut attack, where the safe area is underneath the sphere. Stand under a sphere to avoid the attack.
End of Days targets a random player with a line stack marker. Unmarked players should stand in the line indicated by the line stack marker.
Circle of Ice will then create tethered ice spheres. Esoteric Fusion will make the spheres move toward each other along the tether. There will be a donut attack centered on the point where they collide, so move to the location where they will collide.
Dark Fire II marks all players with circle attack markers that follow them. Players should spread apart from each other to avoid overlapping each other with their circles.
When they are defeated, there will be a cutscene, and you will be faced with the next boss.
Shadow Flare damages all players.
Height of Chaos is a high-damage attack on the player highest in the enmity list. Players should stay away from the circle attack marker centered on the targeted player.
Dualstar creates fire and ice spheres. They will move toward each other along their tethers. The spheres with the shorter tethers will perform their attack first, so if the fire spheres have shorter tethers, move far away from where they will collide, then after the circle attacks, move to the point where the ice spheres will collide. If the ice spheres have a shorter tether, move to their collision point, then after the donut attack, move far away from where the fire spheres will collide.
Universal Manipulation places a set of status afflictions on all players. Each status affliction has a different duration, and when the status timer runs out, an attack indicator will appear. When all players are targeted with large donut attack markers centered on each player, all players should stack together to avoid overlapping each other with their donut attacks. When all players are targeted with circle attack markers, all players should spread apart to avoid overlapping each other with their circle attacks. When a random player is targeted with a stack marker, unmarked players should stack together with the marked player. When chain markers appear above all players heads, each player should run away from the player that is chained to them, until the chain is broken.
Entropic Flame targets a random player with a line stack marker. Unmarked players should stand in the line indicated by the line stack marker.
When the boss casts Arcane Revelation, an Arcane Sphere will appear in the center of the area, and a gauge will appear on screen. Attack the Arcane Sphere while dodging the many attacks that occur at this time. Players will be randomly targeted with line attack markers. Dark Fire II targets all players with circle attack markers. Spread apart to avoid overlapping each other with the circle markers. Dark Blizzard III is a set of cone attacks from one of the shades that appears.
After the Arcane Sphere is destroyed, or after a certain amount of time, the boss casts Annihiliation, damaging all players. The higher the gauge, the stronger this attack will be.
Ancient Eruption targets all players with circle attack markers. Move out of the attack markers to avoid the attack.
Completing the Quest
Defeating the boss will complete one of the quest objectives for the Main Scenario Quest Aetherochemical Research Facility. Afterward, there will be a cutscene. This one is important, so it is recommended to watch it either now or via the Unending Journey in an inn room.