Tenebrous-ZD is a decent-sized planet, only slightly smaller than Earth, and is prominently marsh where it isn't ocean.
It is the third planet from it's star, Tenebrous-Z, a white main sequence star.
While the planet supports life, the environment is harsh and living there is difficult. The weather is just about always humid, and depending on which biome one is in, can be unbearably hot or unbearably cold. However, the marshes hold a lot of useful resources if you look past the dangerous wildlife and difficult climate. The sapient lifeforms on the planet are a race of aliens that humans have dubbed ‘Swamp Harpies’- what they call themselves is unknown, as any attempts to contact them have ended poorly. Tenebrous-ZD has 85% of Earth’s gravity and the atmosphere has a higher oxygen content, which has resulted in the native lifeforms being a bit bigger than what a human might be used to.
Very little is known about the planet as of right now, but given the circumstances of the Astartees, more might be figured out in time.