Blu-Mar Star Trek Adventures
The expanse is on the far side of Klingon space in unclaimed teritory. Klingons give it a wide berth as they view it as a place of dishonor. It's a remnant of a weapon the hur'q used to show their power when they occupied Kingon territory. Several Klingons who have accepted discommendation have traveled to the expanse to live out the rest of their lives in dishonor. There are also rumors that pockets of Klingons still affected by the Augment virus may be living here.
The Federation, with permission from the Klingon Empire, has been mapping this region. Several deep space probes have found planets rich in desirable minerals. An agreement is being worked out between the Klingons and Federation to mine and share the minerals. There have also been indications of cosmic phenomena unique to the region. Further study is warranted.