Daelkyr

Daelkyr are insane totally-not-Lovecraftian Outsiders from Xoriat, the realm of madness. They invaded the Eberron something like 9000 years ago for reasons unknown to anyone (probably including themselves) and caused one of the most horrific conflicts in the history of Khorvaire. While few in number, daelkyr are powerful to an almost godlike degree, capable of reshaping reality on local level, reforging the forms and minds of creatures with a thought, barely contained by time and space so they don't really move in the way sane creatures can comprehend, looking like they teleport (they don't, they time-travel to move, don't ask how). And yet they are technically mortal and could be killed. Which is actually an advantage in Eberron cosmology, as all true immortals are unchanging and cannot learn. Daelkyr can and do learn and change, which makes them even more dangerous. No one knows what they really look like - those who've seen them described them as angelically beautiful humanoids clad in living armour, but everyone sees them as members of their own race. Some tried looking on them using True Sight to pierce through this glamour and every one of them instantly went insane.

Daelkyr are the source of almost all aberrations in Eberron. They created illythids by mutating Gish they kidnapped from the astral plane, dolgrims, dolgaunts and dolgarr by mutating captured goblinoids, chokers by mutating captured halflings, neogi and derro by mutating captured dwarfs, and beholders, gibbering beasts and slimes from the sludge that was left in the fleshcrafting cauldrons. Some even say they also created basilisks and medusae - a theory medusae themselves object to vehemently. About the only major aberrations they didn't create are Aboleths who, as always, predate everything. Using their vast and ever growing armies of fleshcrafted horrors the daelkyr waged a war against everyone on Khorvaire, but mostly the Dhakaani empire, who were the most organized and powerful force on the continent. Dhakaani goblinoids fought the daelkyr threat for thousands of years, slowly losing ground and sanity, and it's rumored daelkyr broke the eusocial bond between goblinoids to weaken them. Still, Dhakaani managed to kill a lot of daelkyr until only six of them remained. Unfortunately those six were the trickiest ones with multiple contingencies and proved to be either unkillable or capable of resurrecting themselves. With their empire crumbling around them it looked like Dhakaani would eventually lose, until suddenly some orc druids from the ass end of nowhere started teleporting around and binding the remaining daelkyr to prison demiplanes in Khyber, saving Khorvaire and probably the entirety of Eberron.

In the current days all six daelkyr remain bound to their prison demiplanes, but are not sleeping like similarly bound Overlords and actively scheme to achieve... something. No one sure what, because the actions of daelkyr agents don't follow any sane agenda. Daelkyr are one of the two go-to patrons for insane evil cultists known collectively as "cults of dragon below". Unlike the Overlords they are still active threats as while they are incapable of leaving their prison demiplanes, their armies are free to go in and out. Several wars are currently fought against said armies, most notably below the Mror Holds, where dwarves try to reclaim their ancestral empire, below the Towering Woods, where druids try to contain the biggest portal to Dyrrn's prison, and under Xendrik where Umbragen Drow fight for their survival. Another major hot-spot is the Shadow Marches, the aforementioned ass end of nowhere from where the orc druids that saved the world came from. Those druids called Gatekeepers are still busy keeping daelkyr locked as almost half the orc tribes in the marches are worshiping the Lords of Madness and want to set them free, keeping Shadow Marches in a constant tribal war.

Known Daelkyr

• Dyrrn, the Corruptor: the grand daddy daelkyr, the patron saint of Getting Shit Done and arguably the mightiest of its kind (or at least of those who invaded Khorvaire). All those humanoids corrupted and turned into aberrations? It's their doing. The plague of Silence that broke the Dhakaani empire? Theirs too. All three major current wars against daelkyr? All against Dyrrn's armies. Most other daelkyr see themselves as artists or scientists, but Dyrrn is the conqueror. Mind Flayers and Dol worship it as their divine creator and call it the Overmind. Yes, Illithids WORSHIP the guy. It's also credited with creating the Clone spell. Goblins are certain they killed it during the war. Which they might be right about, but considering this is the guy who invented cloning spare bodies for your soul to shunt into in case you die...

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• Belashyrra, the Lord of Eyes: the daelkyr obsessed with secrets and visions. It created beholders and beholderkin, although there's no love lost between them and their creator with most of them fucking off and doing their own thing when Belashyrra got locked in its prison demiplane. Belashyrra is one of the most popular patrons among the cults of Dragon Below, granting them powers of vision and eye ray magic in exchange of their sanity.

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• Kyrzin, the Prince of Slime: the guy responsible for creating all the slimes and gibbering beasts. Orc cultists of Shadow Marches mostly worship this guy and it grants their followers powers over disease and poison, both to inflict it and cure it.
• Orlassk, the Lord of Stone: the guy credited with creating all the monsters that can turn flesh to stone. You probably should not mention that to any Medusa as they consider this theory heretical. Its cults are rare and are mostly Wizards of Transmutation as it grants their followers increased understanding of transmutation magic. It managed to bind their prison to a giant gargoyle and is generally content with traveling and messing with people in deep Khyber, not interested much in the world above.
• Valaara, the Crawling Queen: the daelkyr responsible for creating most of the monstrous insectoids and insectoid symbionts. Canon materials haven't said much more about it, but Keith Baker's Exploring Eberron, which most fans pretty much take as canon, does go a bit more in-depth. Her minions unsurprisingly mostly consist of buglike creatures, and her humanoid worshipers often fall under the delusion that they are insects transformed into or trapped in a humanoid body or that they are being controlled by parasites.
• Avassh, the Twister of Roots: the daelkyr credited with creating monstrous plants. Again, not much above that.

Daelkyr creations

• Dol - the most mass-produced of daelkyr aberrations, Dol are (at least initially) made of goblinoid stock and form the backbone of their armies.
  • Dolgrim is made of two goblins smacked into one, so they have two sets of arms, eyes and mouths, as well as two brains, but their legs and torsos are fused together. Unlike most other aberrations, Dolgims use armor and weapons, typically armed with a shield, spear, morning star and hand crossbow. Despite having two brains, they're not particularly bright and require supervision from more intelligent aberrations in order to use tactics more advanced than zerg-rushing the opposition and overwhelming them with sheer number of attacks.
  • Dolgarr is made of a Bugbear pumped with growth hormones, then flayed and his hide grafted back inside-out. Dolgarrs live in constant pain, only slightly dulled when they cause pain to someone else and are covered in skin fat and puss which makes them slick and somewhat resistant to fire. They're archetypal "dumb brutes", but with an unhealthy dose of body horror on top.
  • Dolgaunt is made out of heavily mutated hobgoblin. It grows a pair of of tentacles out of the back and have no eyes, instead relying on hypersensitive tines covering it's entire body, granting it blind-sight. Dolgaunts are highly intelligent and are usually commanding hordes of other Dol or even other aberrations. They don't use armor or weapons and instead hone monastic fighting skills, which are further improved by their 360° "vision" and ability to suck moisture out of their victims with their back tentacles, hurting the foe and rejuvenating themselves.
• Chokers were originally created from Talenta Halflings, and are not solitary ambush predators like in other settings, but scouts and sentries for daelkyr armies.
• Illithids were created way before the invasion into Khorvaire by mutating Gish from Astral plane. They usually serve as elite strike teams and commanders of daelkyr forces. Unlike in other DnD settings, Illithids of Eberron don't form hives and are strictly part of daelkyr armies, although they still use mind-controlled slaves and a variety of Ceremorphs. Curiously, Ulitharids in daelkyr armies outrank Elder Brains, and Neothelids are not hated but used as siege beasts.
• Neogi are about the most mutated of humanoids-turned-aberrations and are made off Dwarves. They're not as terminally xenophobic as in other settings and in fact are made to be a support faction, running logistics and trade for daelkyr armies. Neogi psyche is made out of 100% greed (making them supreme anarcho arachno-capitalists) and they're purpose made to see daelkyr symbionts as the most valuable commodity. Even though they have absolutely zero loyalty to the lords of madness that created them, they fulfill their task nonetheless, running slave raids on surface world or even trading with surfacers (usually through mind-controlled or cultist intermediaries).
• Beholderkin - were created as magic artillery and some are still used as such in daelkyr armies, but after their creator get trapped most went on their own, being just as paranoid and xenophobic as in other settings and only kept in check by beings more powerful than them.

In addition to the above creatures, which are canonical and have been canon across multiple editions, Dragon Magazine #348 features the 3e article "Horrors of the Daelkyr", which presents six more minions commonly used by the Daelkyr that still plague Eberron today, although they range from lesser denizens of Xoriat summoned to Eberron to the traditional mutants. These "apocryphal" daelkyr-minions are:

• Akleu: Xoriat natives that look like a humanoid shark with translucent skin and too-many joints in their arms and legs. VIcious, sadistic pack-hunters with incredible agility and a fascination with gems.
• Dolgrue: An alternative to the Dolgarr, this mutated bugbear was created as a heavy assault trooper, with a bestial muzzle, giant crab claws for hands, and bony plates growing through its skin. Like the Dolgarr, it exists in constant pain.
• Kyra: Another Xoriat native, resembles a Huge-sized disembodied brain and spinal column/tentacle suspended by eight bat-like wings. Unlike these other apocryphal daelkyr minions, they are pissed at the daelkyr for getting them stranded on Eberron when Xoriat was sealed away, and now work against them. They still hate all life, they just hate the daelkyr more.
• Opabinia: Originally a tiny, primeval aquatic arthropod, now grown into a giant beast used as an amphibious attack animal. Is actually based on a real-life primordial crustacean and looks almost as weird, but now has dozens of tiny legs to let it crawl about on land. Fun fact; the opabinia previous appeared in 2e in the article "Creatures That Time Forgot" in Dragon #204.
• Xenostelid: A nightmarish amalgamation of giant scorpion, giant spider and giant centipede engineered by the Daelkyr as a living siege weapon.
• Xorbeast: A monstrous ooze-dripping many-mawed thing that was created to capture humanoids and animals to serve as fodder for the Daelkyr's experiments. Noted to be so disgusting that even the Daelkyr find them repulsive.