Return of Xoriat
The daelkyr are extraplanar creatures that are native to the realm of Xoriat. Daelkyr are said to look like extremely beautiful and shapely humans, but with a hint of madness in their eyes and chitinous armor covering their bodies.
They are responsible for most of the aberrations in Eberron, including beholders, dolgaunts, some symbiotic creatures, and many other aberrations.
The daelkyr attempted a planar invasion during the time of the Dhakaani Empire, releasing hordes of their aberrant creations into the material plane. It took an alliance between the goblinoids of the Dhaakhani empire and the orc druids of The Gatekeepers to repel the invading daelkyr, cutting off the plane of Xoriat from Eberron and sealing the remaining daelkyr and their servants within Khyber.
At least six daelkyr remain on Eberron, though they have yet to make a unified attempt to free themselves from Khyber or to restore the connection between Eberron and their home plane. Immortal, the daelkyr are endlessly patient and, as the lords of the realm of madness, their goals and motivations are unfathomable.