Irregular World
Some planets exist outside of the typical description of a (mostly) spherical mass of gases or silicate rocks and metals. These irregular worlds come in a variety of shapes, many of which are still considered theoretical. Some worlds might be artificially designed in the shape of a torus. Other worlds, like a planet in the form of a cube or a world that is entirely flat, exist as the result of cosmic abnormalities or the direct intervention of the divine.
Source
Core Rulebook pg. 394