Kasthezvi
Kasthezvis are malicious, enigmatic, ancient, utterly silent aberrations dwelling in the depths below Kaer Maga.1
Appearance
A kasthezvi looks like a misshapen humanoid with dry, cracked skin, an unnaturally-angled neck, and an asymmetrical, silently screaming face. A vibrating bone crown floats above its head. Its movement is deceptively lurching and uncoordinated. A kasthezvi is six feet tall and weighs 100 pounds.1
Ecology
Kasthezvis' bones are vessels for primordial words of power, which they cannot utter, since their long-departed creators designed them to be utterly unable to cause any sound. Their crowns are believed to suppress magic and allow kasthezvis to speak powerful words without imploding, but no intact crown has ever been recovered for study. This magical dampening effect has weakened over centuries, allowing kasthezvis to draw power from the words and silently utter words of sundering that can level buildings, and some caulborn claim that kasthezvis have also spoken other words with different destructive effects. A kasthezvi could cause calamitous damage if allowed to properly pronounce its words of power. When a kasthezvi dies, it explodes in a burst of suppressed sound.1
Kasthezvis are biologically immortal but cannot reproduce, and learning the secret of procreation might be their biggest desire besides harnessing their primordial words of power.1
Habitat
Kasthezvis inhabit the deepest parts of Kaer Maga. When travelling to the surface, they take great pains to conceal themselves, knowing that their power is greater if no one knows about them. Kasthezvis disguise themselves as mute beggars or Sweettalkers, and very few people notice that they never make a sound; those who do often vanish mysteriously beneath the city.1
History
The origin of kasthezvis has been long forgotten. Only the caulborn know of their existence, and they cannot agree on whether kasthezvis were created as weapons or were originally benign creatures that turned evil due to the suffering caused when their creators departed.1
The first Thassilonian runelord of greed, Kaladurnae, made a deal with kasthezvis: they taught him knowledge about Kaer Maga and snippets of powerful words, and he in turn taught them writing and trained a few kasthezvis as wizards, who became known as runespeakers.1
Society
Kasthezvis hold contempt for all living things and only the smallest respect for the powerful. Some caulborn speculate that the kasthezvis are preparing to unleash a silent cataclysm to destroy Kaer Maga; others believe they seek to refine their words of power or reproduce with surface dwellers.1
Kasthezvi runespeakers hoard arcane knowledge and only leave their lairs on the possibility of learning new secrets. Kasthezvi lairs are covered with glyphs and the occasional silent explosive runes inscribed by runespeakers, which have never been deciphered by others who seek to learn about their history and culture. Kasthezvis communicate in a sign language involving contortions and jerking limbs.1
Caulborn frustrated by their inability to understand kasthezvis sometimes hire adventurers to infiltrate kasthezvi lairs to study them. All such missions have so far failed.1