Ancients

The Ancients are an extinct Major Race that seem to have inhabited most of Charted Space around 300,000 years and are now only known from scattered ruins and artefacts.
They appear to have possibly been bipedal and around human sized, although no remains of an actual Ancient have ever been found (or they were so alien that we don't even recognise their remains, or they didn't have a physical presence).
Many of their ruins and artefacts exhibit extremely high technology, which makes them of extreme interest to modern races. Almost all Ancients sites within the Third Imperium are under Imperial control and planets with Ancients sites normally have Amber or Red travel classifications.
The age of their civilisation is based on dating of sites and artefacts - no Ancient writings or calendar have been identified. The age of Ancients sites is remarkably consistent, which leads to theories that their civilisation may only have existed for around 20,000 years. Damage to sites appears to support a hypothesis that their civilisation met a violent end (which is also thought to have resulted in the high incidence of planetoid belts in Ancients space). This was either a civil war with no survivors, or they were exterminated by an unknown and even more powerful civilisation, of which no trace remains.
The Ancients are commonly regarded as having transplanted Humaniti, Droyne and Vargr (and possibly Aslan) from Terra/Sol to numerous other systems throughout Charted Space, for unknown reasons. The origins of both Humaniti and Vargr (and possibly Aslan) on Terra/Sol has lead to one hypothesis that Terra/Sol or a close-by system was the original Ancients Homeworld.

EXTINCT