Hephaestus, the second planet in Olympus, is covered by hundreds (some estimates claim 400) of Volcanoes, most of which are in a state of constant eruption. This constant activity is caused by gravitational stresses on the planet by the two giant gas moons (Vulcan and Io) that orbit it. Although uninhabitable, it was found that the planet was rich in minerals. A space station named The Forge is in orbit between Hephaestus and its moons that is used to process what is mined and collected from the planet, as well as house the crews that mine the mineral-rich molten rivers.
Hephaestus has two moons, Vulcan and Io.