Penumbra

Penumbra planets have almost no sunlight, and this is their defining characteristic. The surface is often covered in a bit of a humid mist, with a strong plethora of plant and animal life. Trees comprised of Energy Wood can also be found on the surface.

These worlds are a sole source of Penumbrite Ore. This ore is glowing, so it can be easily be found underground. '''Warning! These worlds contain weather and/or biodiversity that may cause psionic collapse. Proceed with caution on these ancient planets.'''

Appearance
These worlds are very dark, but often lit up with bioluminescent plant life. However, bringing a flashlight or torches is recommended. The surface is often comprised of Umbral dirt, a dark and easily-mined substance that proves useful when extracted from. It's also common to find black tar here, both on the surface and underground. These planets are almost oppressively dark, and can often be identified on the star map just by looking for planets using black and other dark colors.

They have been seen to commonly orbit dark stars but they can spawn anywhere, orbiting any star.

Codex description

 * Sunlight rarely penetrates penumbral atmospheres. Rich sources of Penumbrite Ore detected.
 * Penumbra planets have a unique makeup that blocks light but not UV. They are the sole source of Penumbrite Ore.
 * Dark, but with plenty of bioluminescent fauna, penumbra worlds are the only known viable source of Penumbrite.