The Serene Sea is an inverted Traverse: a close concentration of stars that is not made of healthy G and F class stars but out of sequence stellar remnants: white dwarfs, neutron stars, planetary nebulae, stellar black holes. And contrary to the Traverse, there is little doubt about the unnatural nature of this region. Someone went here and engineered the local stars.

In the Serene Sea, there are virtually no habitable worlds, except for Draugr, the "vampire planet", an earth-like world orbiting a neutron star, by all accounts a planet that should not exist. The main human settlements are stations installed at the edge of the region, accounting for a few million inhabitants, the vast majority of which are scientists, historians and pilgrims.

Pilgrims, because the Serene Sea is also a necropolis where dead stars neighbour derelict megastructures and wrecks lost in deep interstellar space. This region is the seat of humankind's first contact with what is known under the generic name of the Sequence: the ghostly remnant of what has once been a galaxy-spanning empire, spreading between the stars at sublight speeds for millions of years. Due to a state of constant war with the Sequence the region is under the loose control of Algorab. 

The Sequence remnants populate the Serene Stars and make them a strange, unfamiliar but also fascinating place. Ancient Sequence megastructures perturbation or even intercept geometry translations. Enigmatic ships lead incursions against human settlements. Hints at an unknowable history are littered across the region. Both the historical graveyard of an impossibly old empire and low-intensity warzone, the Serene Sea is the closest human space has to a frontier.