The Grand Cosmos

The Grand Cosmos is a 4-man dungeon introduced with Final Fantasy XIV: Shadowbringers. It is Trust system compatible.

Lore
Long ago, on the far shore of the Source, a great palace was built by the elves─the Grand Cosmos, an edifice of such magnitude it was said to inspire envy in both the heavens for which it was named and the flowers that pervade its boundless gardens. As with so many wonders of the world that once was, its radiance quickly faded in the wake of the Flood, its halls falling silent, the throne sitting empty. That is, until the palace was given new purpose when a mage claimed it as their sanctuary, their only company being solace, solitude, and the legion of familiars barring entrance to any foolish enough to seek an audience.

Quests
The following quests take place in The Grand Cosmos:
 * A Grand Adventure

Seeker of Solitude

 * Shadowbolt - Tankbuster
 * Immortal Anathema - Party-wide damage
 * Tribulation - Five small circles appear around the room that create puddles shortly after appearing. Any player in the puddle will receive 15 second Heavy and Bleed debuffs.
 * Five brooms will appear on the sides of the room and will move in to sweep up the puddles. Getting hit by the brooms causes damage, a stacking vulnerability up debuff, and a knockback.
 * Dark Shock - Two large circles appear. Move out to avoid damage.
 * Dark Pulse - Stack mechanic.
 * Dark Well - Follows Dark Pulse. Each party member receives a circle AoE. Spread out to avoid overlapping.

Leannan Sith

 * Storm of Color - Tankbuster
 * Ode to Lost Love - Party-wide damage
 * Direct Seeding - Tiles of the room turn green and drop Leannan Seeds. Players need to pick these up and move them out of the green tiles.
 * Gardener's Hymn - Turns any remaining Leannan Seeds in green tiles into Lover's Ring mobs.
 * After a while, Lover's Ring mobs will do a long cast of Toxic Sprout.
 * The second time this is cast, a large green creature appears on the side of the room and will cause a knockback. The knockback is approximately 1 tile in length and affects the Leannan Seeds as well, so the seeds should be placed appropriately.
 * Ode to Fallen Petals - Room-wide AoE. Move under the boss to avoid.
 * Ode to Far Winds - Large circle AoEs appear around the room and each player receives a circle AoE. Spread out and avoid the large circles.

Lugus

 * Scorching Left - Position on the right side of the boss to avoid the AoE.
 * Scorching Right - Position on the left side of the boss to avoid the AoE.
 * Otherworldly Heat - Targets party members and drops a cross-shaped AoE upon expiring. The AoE deals damage and applies a vulnerability up debuff. These AoEs will damage the objects around the room, so be sure to drop them away from the objects as the objects are needed for Mortal Flame.
 * Shortly before the second Otherworldly Heat is cast, three small circle AoEs will appear and Crystal Chandeliers will drop to the ground. Again, these objects should be avoided when dropping the Otherworldly Heat AoEs as they are needed for Mortal Flame.
 * Mortal Flame - Applies the Mortal Flame debuff which deals damage over time and will kill the player when it expires. Transfer the debuff to one of the objects or chandeliers in the room to avoid death.
 * Fire's Domain - Players will be marked with 1-4 swords. Lugus will charge each player in order and cast Fire's Ire. If the player is too close to the boss during the charge, they will receive a vulnerability up debuff.
 * Fire's Ire - A cone AoE.
 * Culling Blade - Party-wide damage
 * Captive Bolt - Tankbuster