Intact buildings in The Onyx City

The place where the chief sorcerer of the Greys (now a demilich or some such) still labors to summon Yog-Sothoth to open a conduit to the homeworld directly.  A cult has formed around the Grey Sorceror devoted to these ends.

A giant store of knowledge of the Greys, in giant vats of a thick fluid filled with tiny crystalline beads suspended throughout.  These are basically mass storage devices full of mind-destroying knowledge.

A giant warehouse full of crates and robots moving them about endlessly.  Most are empty, because everything had been gone through, and what remains may be dangerous or incomplete.

A lot of anti-grav gear may be found here, which helps in moving cargo (or treasure).

A place where the needs of The Onyx City were made.  As supplies stopped coming through the Skein things here started to go pear-shaped or breaking down.  Now it’s a sea of complicated machinery that doesn’t work (or malfunctions), strange vats of dangerous fluids and repair robots trying to get everything under control.

A place where clairvoyant viewing of different endpoints in the Skein may be seen through special apparatus.

A giant tower that is an interstellar transmitter, which the Greys used to try to contact home after the connection to their world in the Skein collapsed.  A ship was sent before in response, but crashed (see hex map) and no further contact has been made.

The transmitter is currently not operational, but if reenabled it could signal to the homeworld to send yet another craft, thinking that the colony on Thule was still operational.  Of course, it would take some time.

Much of Grey technology is built around crystals; this is where the crystals are grown.  You may find robots, constructs and crystal-eating monsters exist here.

A cluster of several fortified, heavily armored onyx blocks, each roughly the size of a small house, with no visible doors or windows. Deep scoring or stress marks scar their outer surfaces, hinting at immense forces once contained within. These were likely used to house dangerous or volatile specimens, perhaps creatures brought through The Skein or the results of forbidden biological experiments, now silent but potentially still holding a terrifying legacy.

Clusters of small, perfectly sealed, cuboid onyx domes. Inside, faint, unsettling humanoid or alien shadows can sometimes be seen flickering against the inner walls, hinting at telepathic research, communication, or even dream-weaving.

A central, sunken onyx plaza with numerous recessed bays and automated tracks carved into its floor. Hundreds of small, inert maintenance or reconnaissance drones, made of lightweight onyx and dark metal, lie scattered, perfectly preserved but unresponsive.

A multi-layered onyx structure with perfectly smooth, sterile internal chambers. Empty, clear containment cylinders, now covered in dust, line the walls, suggesting the storage of biological samples or genetic material from diverse worlds encountered through The Skein.

May have lots of weird encounters here from beasts that were contained or isolated here.

The central control nexus for The Onyx City.  Looks a bit like an air traffic control tower, may be the place to go and enable access for all those places you want to get into, but you need top-level clearance to get inside first.

A cluster of perfectly smooth, highly polished onyx structures, some resembling massive, upturned bowls, others sleek, elongated tubes. The air around them sometimes carries a faint, metallic scent. These were likely medical or biological facilities, where the Greys underwent physical modifications, healing processes, or perhaps adapted their forms for travel through the diverse environments encountered via The Skein.

A massive, dome-like structure of seamlessly fused black onyx, almost perfectly spherical, deeply embedded in the ground. Its surface is crisscrossed with thick, glowing (now dormant) conduits that lead into the earth and connect to other major buildings. This was likely the city’s primary energy generator or central power distribution hub, hinting at a vast, interconnected network that once hummed with life.

Expansive, low-slung complexes of repetitive, modular onyx units, interconnected by smooth, enclosed walkways. Each unit is a featureless cube or rectangle, with internal configurations that suggest highly efficient, standardized living or communal spaces. The sheer scale implies a large former population, now eerily silent.