The area between Borshall and Geled, called the Transgeled, was the very last area to fall under the control of the First Terran Empire, and it proved trouble for the next four hundred years.
It is surprising that some of the stronger Emperors and Empresses (particularly Maj Thovold) did not organize the area as a ninth province and put an Imperial Capital on, say, Tep Kecor or some other planet. But the Imperial position was highly dependent on the Nobles, who were jealous of position and consequently would not favor the establishment of a new province.
After Karphos, the Transgeled fell to the Patalanian Union rather quickly and by the First Sack of Terra (381) it was lost to the Empire. Although Geled made moves to recover it, the Transgeled remained wild, providing a starting point for the Volkerwanderung of the 6th, 7th and 8th centuries TE.
Through the Interregnum, the Transgeled remained a wild and dangerous region, a constnt battleground of unstable states.