Dalamud

Dalamud is the smaller of two moons orbiting Hydaelyn in Final Fantasy XIV. Originally, the moon was colored white, but recently its color has changed to red and citizens of Eorzea can already notice it becoming larger by the day. This change is said to be affecting sea currents, crops, and even the behavior of monsters and their size. It is the most prominent figure in the Seventh Umbral Era story arc. Main antagonist Nael van Darnus seeks to use it as part of his plan to destroy and purify Eorzea.

Story
Due to this noticeable change on the moon, as well as the prophecies regarding the Seventh Umbral Era, Cid nan Garlond believed the Garlean Empire was using its magitek technology and forbidden arts to use Dalamud as a Meteor of sorts to purge Eorzea of its "taint".

In a later scene, the player was able to use the echo to see the past of a Gridanian Conjurer who eavesdrops on a talk between Nael and Gaius van Baelsar, where the former was trying to convince the latter to use Meteor on Eorzea. However, Gaius was hesitant to follow the idea, as the Garleans had not discovered how to control where Dalamud will fall if the spell was used.

Later events confirm that Nael had succeeded in initiating Dalamud's fall to Hydaelyn. The Garlean stronghold Castrum Novum released in Patch 1.22b contained a Lunar Transmitter guarded by a Imperial Soldiers and Magitek automatons. This transmitter had locked Dalamud's descent over Eorzea, specifically over Mor Dhona. Adventurers from the now-allied Grand Companies of Eorzea were able to destroy the transmitter within the stronghold, only to learn that Nael no longer needed it. He then connected with Dalamud, becoming empowered enough to control it himself, and disappeared.

He was tracked down over Coerthas after his disappearance during the events at Castrum Novum, and he used the ancient Allagan technology to control Dalamud, bombarding a platoon of soldiers with "Lunar Fragmens". In response, the Eorzean Alliance sent a party to meet him at his floating platform, "Rivenroad". Here he explained his plan to use Dalamud to purge Eorzea entirely, beyond and in spite of Garlemald's desire to conquer a viable land. After his apparent defeat, Dalamud empowered him once more, transforming him into Nael Deus Darnus. This was not enough, as Nael was destroyed by the Eorzean forces, but Dalamud continued to descend.

At first it caused luminous auroras and shooting stars throughout the skies, but as it breaches the atmosphere all other weather disappeared. Day and night were only barely distinguishable beyond the gray clouds and the burning red form of Dalamud, later accompanied by flashes of lightning.

"Impact"
An Impact Counter was added to the game's launcher, indicating that it would land midnight (PST) of November 11th, 2012. In the End of an Era video launched just after the servers were shut down, Dalamud was revealed to contain a massive dragon as big as any City-State. This was revealed later to be the dragons' trapped Primal: Bahamut. This will be further explained in A Realm Reborn, likely related to the Great Labyrinth of Bahamut.

Lambs of Dalamud
The Lambs of Dalamud are a cult that sprang up when Dalamud first began showing signs of its descent. They believe that the scent of fresh blood will attract "Menphina's Loyal Hound" and bring it down upon the land to purify it. For this reason they have sent followers to the city-states of Eorzea to lure adventurers to their dooms under the pretense of having them save kidnapped family members.

Though some of its members are known to use swords, the Lambs are predominately Thaumaturges who use the blood of their sacrifices to generate their spells.

The Lambs of Dalamud do not fear death, believing that Dalamud will recognize their sacrifice and descend into the Gates of the Seventh Hell to resurrect them as servants in the Seventh Umbral Era. Their last known ritual was practiced in Gwyr-Aen, coincidentally where the symbol of Menphina appeared, before an adventurer slew them. They accepted their deaths readily upon realizing that they gave their own blood in service to Dalamud.

Appearance
A consistent part of each update involves making Dalamud appear closer in the sky. In 1.19 and 1.20 the change could easily be overlooked, but thereafter it has grown to a size that is impossible to miss when the skies are clear, larger the sun. It appears deep red against the blue of day or black of night - it orbits in sync with the planet's rotation. It is locked in its descent on Eorzea.

The closer one looks, the more its artificial nature becomes apparent. Clips of it in the trailers and the view of it in the battle for "To Kill a Raven" show its mechanical features more clearly. Nevertheless, the "Lunar Fragments" with which it showers the planet are chunks of burning rock.

Dalamud is also depicted in the symbol for Menphina as the smaller circle overlapped by the larger Moon circle.

Trivia

 * A nearly identical scenario to Dalamud's fall appears in Final Fantasy IV: The After Years in which a red moon, not the planet's main moon, threatens to crash to the planet.
 * The Astrolabe, a staff made only by the most skilled Goldsmiths and restricted for use by Level 50 Thaumaturges, is, as its name implies, a celestial model depicting Hydaelyn, with moons Menphina and a tiny red Dalamud orbiting. In this model, the two moons swing around Hydaelyn via magic. It should be noted that the model's moons act independently of each other, even though before 1.19 Dalamud appeared leashed by Menphina's gravity as a static part of her being.
 * Dalamud is referred to as "Menphina's Loyal Hound" by NPCs due to its relationship with the larger primary moon.
 * Dalamud was always in the southeastern sky during its descent, no matter what part of the continent the player views it from. One would expect its position to change with perspective while it was closer to the land, but it appeared to be falling southeast of Thanalan, possibly in the Sea of Ash just south of Ul'dah. During the End of an Era video, however, its true position is clearly over Mor Dhona, as an object fell from it and landed on the battlefield.
 * "Dalamud" and "Bahamut" are phonetically similar, with only a few consonants changed. This is likely because Dalamud served as Bahamut's container, although the exact reason is unknown.
 * Dalamud would have a different role on the game's original storyline. A familiar star shower appeared during each nation's main scenario quest. However, once Naoki Yoshida decided they would close the original version with an "End of the world" scenario, he asked if it was okay to "bring it down".