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Nisis consists of a clay core surrounded by a liquid water ocean with more fresh water than all of Golarion. This water accounts for most of Nisis' mass and is, in turn, surrounded by an icy crust. The average temperature on Nisis' surface, which is its coldest region, is −30 °F.1
Soon after the destruction of Damiar and Iovo, the early sarcesians discovered Nisis, a naturally occurring asteroid with enough space to house all of them. They rejoiced and began transferring their aquatic members to the sea and adapting some of the terrestrial ones to live under the surface.1
However, soon enough, the settlers discovered that Nisis was already inhabited by strange predators that swam up from the darkness to hunt them, leaving behind only clouds of blood.1
To this day, nobody knows the true identity of the predators that inhabit Nisis, whether they originated as underground dwellers shielded from destruction by rocks, or animals mutated by the magical cataclysm. Since the sarcesians breed slowly and cannot afford a prolonged war against them, they have mostly retreated to the well-lit shallows under the ice, leaving the deep dark to the predators.1