Twilight dragonflight

The twilight dragonflight is a dragonflight created by the results of magical experiments carried out by Sintharia upon dragon eggs. Using ancient dragon artifacts and the powers of the nether dragons, Sintharia created a new breed of dragons that feed vampirically on all forms of mystical energy. The first encounter of these dragons with the outside world was by Krasus, Kalec, and the draenei priestess Iridi. Iridi thought of their appearance not as a shadow, but more akin to the day turning to night, like twilight as experienced on Azeroth. She thus dubbed them twilight dragons.

While Sintharia's experiments resulted in very unstable twilight drakes, and Nefarian's experiments resulted in infertile or deformed chromatic dragons, their efforts paved the way for Deathwing to perfect the process of breeding and artificially aging twilight dragons. These draconic aberrations were first seen in-game in Wrath of the Lich King, and became major antagonists in Cataclysm. The twilight dragonflight was thought nearly extinct, most being killed in the war against Deathwing.

During the third invasion of the Burning Legion, it was discovered that the twilight dragonflight survived, with a mature drake named Zeryxia leading them. While Zeryxia was killed, more twilight dragons were discovered within Grim Batol and elsewhere, as stone troggs unearthed deeper caverns wherein thousands more eggs had been laid.

Types
The twilight dragonflight includes the twilight dragons themselves as well as all other twilight dragonkin such as dragonspawn and drakonids.
 * Twilight dragon (mature)
 * Twilight drake
 * Twilight whelp
 * Twilight dragonspawn
 * Twilight drakonid

Night of the Dragon
The twilight dragonflight was first created by Sintharia, aka Sinestra, prime-consort of Deathwing the Destroyer. Eager to succeed where her hated mate had failed and create a new breed of dragon that would rule the world, Sintharia used a nether dragon named Zzeraku, which she captured with a chrysalun chamber, together with two draconic artifacts, to alter several dragon eggs from various dragonflights. The artifacts were an ancient blue dragon relic known as Balacgos's Bane, and shards of the infamous Demon Soul. Thought destroyed by the human mage Rhonin, Sintharia gathered several fragments of the Demon Soul and used the power within them to carry out her designs.

Sintharia's earliest creations proved unstable and were destroyed by Krasus and Kalec. However, they still displayed considerable power, having the ability to vampirically drain magical energy from any source. Sintharia's subsequent creation, Dargonax, proved even more powerful and far more cunning. Dargonax proved too ambitious and strong for Sintharia to completely control, even with fragments of the Demon Soul in her possession. Only the sacrifice of the nether dragon Zzeraku enabled Dargonax to be defeated, and in his death throes he seemingly destroyed Sintharia as well.

Although Sintharia and her creations were all slain, several of her unhatched twilight dragon eggs were taken from her lair in Grim Batol by Deathwing himself. Hiding in tunnels deep beneath Grim Batol, caverns older than any the dwarves had ever constructed, Deathwing had whispered his urgings to the unsuspecting former consort, making her believe that everything was according to her own designs. He safely stored the twilight dragon eggs and began his plans to perfect the new dragonflight, intending to erase the failures of his family and use the newest breed of dragon for his own designs.

Obsidian Sanctum
Deathwing's continued absence led many to assume that Sintharia had been acting alone at Grim Batol, but a recently discovered clutch of twilight eggs inside the Chamber of the Aspects has raised fears that Deathwing himself played a role in the creation of the malefic dragons. A powerful guardian, Sartharion, watches over the eggs within the black dragonflight's volcanic chamber, the Obsidian Sanctum. If the rumors of Deathwing's involvement are true, the dark future that he set into motion seems on the verge of plunging Azeroth into a new age of twilight.

With the red dragonflight already committed heavily to battling Malygos and the Scourge, Korialstrasz sent word of the twilight eggs to the Council of Six in Dalaran in the hope that adventurers could be found to deal with the situation. As he had hoped, a band of heroes was deployed in short order, and the twilight eggs were destroyed. The incident went without fanfare, mention, or acknowledgment; and for a time, seemingly without retribution.

Ruby Sanctum
In order to shatter the Wyrmrest Accord and to crush those that would stand in the way of their master's reemergence into Azeroth, a powerful war party of the Black dragonflight, led by the fearsome twilight dragon Halion and his lieutenants Saviana Ragefire, Baltharus the Warborn and General Zarithrian, had launched an assault upon the Ruby Sanctum beneath Wyrmrest Temple.

A survivor of the initial attack, Sanctum Guardian Xerestrasza believed the true focus of their interest seemed to be the eggs kept there in the Sanctum. The heroes stopped them before they were allowed to succeed.

Cataclysm
The story of the twilight dragonflight is expanded in World of Warcraft: Cataclysm, in the region known as the Twilight Highlands, east of Grim Batol. What Deathwing has planned for them is yet to be known. They seem to be some kind of an elite guard within Twilight's Hammer clan's ranks and their drakes are seen to be used as mounts by their mortal followers.

It is explained that Twilight dragons are usually raised from stolen eggs from other dragonflights, which are then modified through dark magic. A "natural" egg found in Mount Hyjal revealed that one of their matriarchs, Desperiona, has become a viable broodmother.

It is further revealed that the Twilight Brood is being created by a reanimated Sintharia in Twilight Caverns under the Bastion of Twilight. After being slain, Sintharia says: "Deathwing, I have fallen, The brood has fallen", which might mean that her death is the end of the Twilight dragonflight.

During the events of the Dragon Soul, Twilight dragonflight is nearly extinct. Though once vast in number, only a few dozen twilight dragons now remain. Astride these hardened survivors are the last vestiges of the Twilight's Hammer's army: the elite drake riders of Deathwing's personal escort. Led by the insidious Warmaster Blackhorn, they move with unholy purpose, driven to protect their dark master.

Though adventurers seemingly brought down these last vestiges of the flight while pursuing Deathwing, and Blackhorn was slain, it's perhaps notable that his mount, Goriona, escaped.

Heroes who proved their might in the gladiatorial arenas during the Cataclysm were awarded the most exceptional of the twilight drake broods.

Legion
The twilight dragonflight is reborn and joins the Twilight's Hammer in the Twilight Depths of Deepholm. They were led by the dragon Zeryxia, who answers to Sintharia's whispers from beyond the grave.

Battle for Azeroth
During the Fourth War, numerous twilight dragons, drakes, and dragonkin can appear on Island Expeditions, apparently drawn by the Azerite being mined by the Horde and Alliance. An adventurer can bring a Battered Twilight Scale to an agent of the red dragonflight, Eryna, who reveals that the troggs dug too deep and disturbed a previously-unknown massive cache of twilight dragon eggs below Grim Batol. Eryna claims that she can sense thousands of heartbeats below Grim Batol, but she has no idea how many are truly down there, or where other caches might exist. She also saw them coming out of the citadel, being mobilized by someone.

In the Vermillion Redoubt in the Twilight Highlands, Void-twisted twilight dragonkin have surrounded Alexstrasza, but a champion and Kalecgos arrived and helped subdue the invaders. A twilight dragon Vexiona is confronted in front of Grim Batol who before fleeing states "Your pathetic dragonflights will fall. If you will not serve the master, then I will find one who will". Twilight Whelplings re-emerged outside of Grim Batol.

Visions of N'Zoth
Vexiona, accompanied by Velinaria and Dreliana, leads a band of Darkwhisper cultists in an assault on Blackwing Descent in an attempt to lure in and capture Wrathion, with the hopes of using his essence in a ritual to raise Onyxia and Nefarian as servants of N'Zoth. Not all Twilight Drakes seem to hold their master's favor, as when Wrathion descended into Blackwing Descent, he found a drake, nearly dead from maiming by the Old Gods' forces by their experiments to augment them. This drake later aided the group against their former masters, going as far as to ferry the bearer of the Heart of Azeroth back to the Chamber of the Heart after they had destroyed the remains of Onyxia and Nefarian and forced Vexiona and Dark Inquisitor Xanesh to retreat to Ny'alotha.

The twilight dragonflight has had a fractured past and now has an uncertain future. Vexiona's clutch of eggs was kept in a chamber inside the Carapace of N'Zoth, exposing them to N'Zoth's corruption from a young age and driving them even more mad than other twilight dragons. However, after N'Zoth's defeat, some of them had their minds cleared by Wrathion with the promise that they, and he himself, will find themselves some day, despite their pasts.

Description
Twilight dragons resemble black dragons, but they glow with a greenish, red, or, more commonly, amethyst light. The earliest twilight dragons created by Sintharia had the ability to feed off of magical energy, particularly enemy dragons. The later dragons, those raised by Deathwing, may have similar abilities.

Twilight dragons also possess the ability to turn incorporeal at will, allowing attacks to pass through their bodies without harming them, though they cannot remain incorporeal indefinitely. This incorporeality is caused by them shifting into another plane known as the Twilight Realm. Strong twilight dragons such as Ultraxion, Halion, and Valiona and Theralion are also able to pull other people into the Twilight Realm with them.

As a flying mount

 * Reins of the Twilight Drake drops from Sartharion in the 25-man version of the Obsidian Sanctum. It drops only if all three Twilight Drakes have been taken alive into the boss fight. It can only be distributed to one person per clear.
 * Reins of the Twilight Harbinger is a reward from the achievement Glory of the Dragon Soul Raider.
 * Twilight Avenger (item) is obtained from island expeditions.
 * Uncorrupted Voidwing is a reward from Ahead of the Curve: N'Zoth the Corruptor.

Speculation
Sintharia's final words in the Bastion of Twilight could have several different meanings. Most associate them with the fall of the twilight flight. However she is also the last remaining brood mother for the black dragonflight after the death of Obsidia. Additionally the twilight dragonflight is also capable of 'reproducing' via the eggs of other dragonflights, meaning Sintharia's death could mean little for the flight in the long run.