The Praxis Ring was a region around the Klingon homeworld of Qo'noS.

Arla Rees was onboard the science vessel Solok which was remapping the Praxis Ring. (DS9 - Millennium novel: The Fall of Terok Nor)

Presumably, from the name, the Praxis Ring is the remains of the Klingon moon Praxis.
Community content is available under CC-BY-SA unless otherwise noted.