The K'daai, known in the dark tongue of the Chaos Dwarfs as the K'daai Zharr, which means Scion of Fire or Fireborn, are mighty daemonic fire-elementals which serve the Daemonsmiths of the Chaos Dwarf Empire.
Chaos Dwarfs are arrogant, malign and paranoid beings who will bend their knee to none but their Father in Darkness, Hashut. The desires of their Sorcerers and Daemonsmiths are for power and domination, and for weapons and soldiers that will make them invincible - and it is from this desire(and by the blessings of hashut that some how didn’t go horribly wrong) that the K'daai Zharr; the scions of fire, were born.
Rather than summon uncontrollable Daemons as a human Chaos Sorcerer might or parley bargains with the greater fiends of Chaos, priests of Hashut have long sought to enslave the Daemon they summon by binding it into weapons and armour, war machines and constructs, thus harnessing and controlling them to the Sorcerer's will and giving them form. With the K'daai they have sought to do something more, to create a race of beings, half-daemon stuff and half-raging fire drawn from the magma of the deep earth and birthed in the boiling blood of Hashut's burning sacrifices, given form and contained within an armoured framework of articulated iron and rune-stamped bronze.
The High Priests of Hashut have succeeded almost too well in the K'daai, for they are almost mindless, elemental forces of destruction, and need to be laid to rest as cold and silent metal until they are required in battle, where they burn bright and terrible, but briefly. Only the greatest of the Sorcerer-Prophets is able to forge these monsters of metal and flame, and the process is both costly and arduous in the extreme. This limits their number, making them almost the stuff of legend. But with the dark imaginings and limits of deadly craftmanship the only end to the terrible forms a K'daai can be fashioned and shaped into, there have been those of Hashut's priesthood who have met their cursed doom early, as the power required to make their glorious vision real has slipped from their grasp.