(Named after a German fresh-water spirit residing in sacred springs or rivers, meaning “wonder” or “sea-fog”)

Melusine is one of the strangest worlds in the Border Ring, offering a one-of-a-kind experience to its visitors. The planet’s atmosphere is an unbreathable environment of almost pure nitrogen and carbon dioxide, with next to no oxygen. However, the planet’s surface is covered in a deep ocean of liquid fluoroalkanes, a type of inert perfluorocarbons. Thanks to undersea gas vents, these fluoroalkanes contain very high levels of dissolved oxygen, much more than human blood. As a result, organisms that normally breathe air can breathe underwater here. After getting over the initial discomfort caused by fluid filling the lungs, both humans and Ghost Children are able to breathe more or less normally. The only downside being that vocalizations are much more difficult – the native Ghost Children exclusively use sign language and humming vibrations to communicate, while most newcomers rely on tablets that they can type out messages on.

Most humans and Ghost Children find it easier to swim through the liquid than to attempt walking along the seafloor; the indigenous Ghost Children are predominantly otter-types with sleek, hydrodynamic bodies, transparent secondary eyelids, webbed toes, and muscular tails to enable them to swim as agilely as if they were flying through air. Others use flippers and other diving gear to help them move, and those with reduced mobility can use motorized propeller-driven “scooters” to get around.

The fluoroalkanes are as non-toxic as water, and no long-term side effects of immersion have been discovered yet. There is even little risk of decompression sickness, since breathing liquid does not cause body tissues to become saturated with high pressure gases. However there are still dangers here – the liquid pressure will crush anyone who dives too deep. Travellers are advised to heed all warning lights, and to stay within marked travel areas unless accompanied by a local guide.

Heat is predominantly geothermal, most lights are chemical or bioluminescent, and power is either geothermal or hydroelectrically generated by currents or tidal action. Like almost all other Border Ring worlds, there is extensive resource extraction on Melusine. Deep-sea mining and gas drilling is prevalent, and there are perennial issues with “water” pollution from these mines. There are also surface-level mining facilities, although this is dangerous work.