Any Other Rock

There is clear evidence that … was at some point inhabited by a sapient species. Ruins that have been found of an industrial age civilization on the cusp of pre-FTL spaceflight.

At some point, however, this civilization was struck with a planet-wide calamity and totally extinguished. Little more than rubble remains, and there are no signs that any protective measures were taken by the afflicted population. The event was not violent or destructive, everything just seemed to... stop. Whatever hit them came as a complete surprise... or, perhaps, they chose not to resist it.

Beneath the ruins of the largest city, an amazing discovery was made! An artificial underground complex of immense proportions was detected by surface-penetrating sensors. The entrance, highly elaborate in design and possibly ceremonial in nature, was easily located, but further exploration was quickly halted.

The two large moons of … exert exceptionally powerful tidal forces, so strong in fact that they affect the motion of magma currents in the planet's core. The underground complex seems to be built with this in mind, with the corridors and chambers periodically flooded with running lava. Luckily enough the ebb and flow can be predicted, but it is as yet a mystery why a relatively advanced civilization would construct a subterranean deathtrap like this.

An expedition was sent down into the volcanic tunnel network. Navigating the magma-scoured basalt maze will be a delicate business, as the frequent ebb and flow of lava periodically maroons the expedition deep within. When - or if - the end of the labyrinth is reached, there is also the long road back that needs to be traversed.

Once inside, there is no way of communicating with the expedition. We can only wait.