Deep Citadel

The Deep Citadel is a massive fortress located deep beneath the moon's surface.

Background
Elsewhere upon the moon is a set of airlock-styled doors, which can only be accessed by a complex set of key codes. Success will reveal a sealed set of caverns, all of which are filled with an earth-compatible atmosphere, kept a temperature relatively - but still slightly cold - to humans and even bearing a stronger sense of gravity - yet still weaker to the pull of the Earth's. The caverns themselves form a labyrinth that stretches for miles on end in twisting and branching directions. Within their walls grow a variety of alien fungi, out which 10% are edible to humans, but separating theme out of the mixture from the incredibly toxic kind will require a success on a level 6 difficulty task. At the very center of a labyrinth is a very large, artificial structure known as the Deep Citadel, which bears hundreds of levels, each connected to the other via a series of gentle, spiraling ramps. Believed to have once been an elegant domain for non-human creatures, all of its interior furnishings are currently missing, with only the walls - though sometimes the ceilings, as well - bearing any décor. The Baroque style of their reliefs and carvings seem to depict reptilian creatures who wield an almost insect-like multitude of limbs.

despite the lack of furniture, visitors may also happen upon the skeletal remains of various creatures, all of which vary in age but have at least been down there many years. Some of these remains actually contain useful tools and devices, which indicate they were intelligent in life, with even a fair number of them carrying life-support equipment, which also suggested that they weren't from any earth-like world. Others theorize that the Deep Citadel housed somewhere within its form a mode of interplanetary travel or that it served as some hub or nexus which led to different locations. Some insist that the Deep Citadel was a nexus for time travel and that the key to the moon's constant time shifts lies somewhere within the structure, possibly even suggesting that the dead remains scattered around its interior are actually those of creatures from other time periods. Unfortunately, however, none of these beliefs have actually been verified yet.

Also within the surrounding caverns are semi-intelligent creatures known as the Ylhathi, who bear a slight resemblance to the mysterious creatures depicted in the architecture as well as to human beings. These long-lived, air-breathing beings have slow metabolisms but have also become cannibalistic but would more than welcome a new source of food. Having once existed in greater numbers, their constant devouring of each other has unsurprisingly, though slowly, decreased their numbers. The ylhathi also possess a range of superstitious beliefs as well as their own rudimentary language. Led by leaders who try to interpret omens in practically everything that happens, they refuse to make their homes within the citadel because of their creed, even though they can still enter and exit it, as they please.

The Deep Citadel of the Past
Just as in the present day, the Deep Citadel and its surrounding, cavernous labyrinth still exit within the distant past of the Moon, with the major difference lying in its ylhathi residents. Unlike the present, the ylhathi are more numerous as well as intelligent. While they might be considered more dangerous, their greater level of intelligence at least makes them less savage and thus open to negotiation.

The past ylhathi, if prompted, may reveal how they remember originally being brought to the underground caverns by the creators of the Deep Citadel, meant to serve as slaves. Their "masters" now long gone, most of what the ylhathi supposedly know about them happens to just be superstitious nonsense.