This is reached from location M16 in Level 9 Labyrinth IV. You arrive at M1 and can return the same way. Read tracks shows nothing and that's because there are few encounters. Those that you will have are minor, hardy clerics, silver ogres and a few wimpy were bears. Anyway, go to K2 and, if you go east, you'll teleport to K8, which will also take you back. At I8, you'll learn you're at the nexus of the Arena. What is the Arena? Evidently, it was a place where, in the time when Arnakkian bestrode the land of Twinion, the bravest warriors and wisest mages could do battle. Four gateways lead each to one staging area - the Red Arena from K8 goes to M4, the Blue Arena from I7 to D4, the Green Arena from H9 to D13 and the Yellow Arena from J10 to M13, each staging area has two doors in and two out, all one way.
To be honest, I have no idea what this section does. I mapped the whole lot, found nothing of use anywhere. Does anyone have any idea why it's here?