Perseus Arm (and possibly also Outer Arm) space-faring predecessors of the Limners.
The Auld Limners were an unknown biological (or possibly biomachinic) species, who built a vast empire that once stretched further beyond the periphery, and they provolved a number of species, including the modern day Limners, who may have been presapient relatives of the Auld Limners. It is known that they interacted with the Soft Ones. Most xenoarchaeologists in the Current Era believe that the Auld Limners were provolved by the Soft Ones, or at least raised from a primitive level of technology. Note that the Soft Ones themselves were probably provolved by the Muuh, making the chain of provolution Muuh - Soft Ones - Auld Limners - Limners.
The Auld Limners used advanced AI systems, including a semi-mythical figure known as the 'Overlord' which may have reached as high as S:4 on the toposophic scale used by Terragens. All available evidence suggests that this entity no longer exists, and may have undergone some form of transaturation ascension that has rendered its current physical location undiscoverable.
All physical remains of the Auld Limner species have been destroyed (possibly during the same event that removed all trace of the Overlord), but from certain stories and legends told by the current Limner species and obscure records held by the Soft Ones and Muuh it seems likely that the Auld Limners resembled the current Limners to a certain extent, but were larger and may have been capable of bipedal locomotion.
The period of the Auld Limner empire, from about 38000 to 20100 BT (usually applied to the Perseus Arm only) is sometimes referred to as the Auldlimnerian Epoch.