The Triplets
A trinary star revolves deep within the Oestalan Sector. The three red dwarves are an extreme rarity in the galaxy, and are high on the investigation priority list of the Mechanicus.
However, in a dance impossible through natural means, a lone planet orbits in a complex pattern around the three stars, a rarity in the galaxy.
Even stranger is the position and measurements of said star. The planet would be optimally heated for human habitation, and never falls out this zone despite the triple star dance.
The planet has no atmosphere and is ravaged by meteoric impacts, but traces of water, vegetation and oxygen-nitrogen atmosphere has been found.
The now-lost Ark Mechanicus, The Copper Blessing sent reports of unusual energy readings in the planetary core, but was ambushed by orks and forced to abort the measurements.