Note: In addition to the information presented here, students should refer to the Emperor's Hammer System Manual located at https://www.emperorshammer.org/sysman/ or on the Emperor's Hammer Wiki. As of July 2022, the System Manual was being migrated to the Wiki.

Osiris is unique among the planets of the Emperor's Hammer in that it is covered entirely by water. The planet's only sentient life for many years was the staff of the research facility there, commonly known as the Imperial Underwater Research Facility (IURF). In recent years floating islands have been created with the use of small repulsorlifts to create a suitable foundation for a sentient population on the planet. The islands are also pontoons, engineered in orbit specifically for the purpose of supporting the islands should the reactors and/or repulsorlifts fail. The planet has moderately dense cloud coverage at most times owing to the simple fact that it is made up entirely of water. Weather only changes on the planet after volcanic eruptions below the ocean surface cause typhoons on some parts of the planet and spew gases into the atmosphere. Because of this, occasional patches of acid rain is common on some parts of the planet, especially those near the Nephthys Fault

The unbroken, flat surface is utterly contrasted by the pitted and gnarled seabed many kilometers below. Submerged canyons and trenches plunge beyond the reach of all but the most advanced submersibles, great spires of rock and ridges jut into the dark waters above, all the result of the planet's constant seismic activity and repeated undersea eruptions from volcanoes and magma chambers.