DS9: Gateways - Demons of Air and Darkness by Keith R.A. DeCandido

Blurb:
Once they moved from world to world in a single step, through innumerable transdimensional gateways that spanned the galaxy. They were masters of space, and to those that feared them, they were demons of air and darkness. But long ago they left their empire and their miraculous technology behind. Now the key has been rediscovered, and all the doors have been flung open.
Open for exploration... or open for invasion. On a world near space station Deep Space Nine, Colonel Kira Nerys, her crew, and some unexpected allies fight to avert destruction on a planetary scale. Meanwhile Lieutenant Nog and Ensign Thirishar ch'Thane search for a way to shut down the portals forever; and behind the scenes Quark plays a dangerous game that could determine, once and for all, who wins control of the Gateways...
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It has been a long time since I read this one, but I remember that I really liked it. Good continuation of the ongoing stories in the DS9 series, one of the stronger entries in the Gateways series and of course the set-up for a very, very strong short story in the seventh Gateways book.
Once they moved from world to world in a single step, through innumerable transdimensional gateways that spanned the galaxy. They were masters of space, and to those that feared them, they were demons of air and darkness. But long ago they left their empire and their miraculous technology behind. Now the key has been rediscovered, and all the doors have been flung open.
Open for exploration... or open for invasion. On a world near space station Deep Space Nine, Colonel Kira Nerys, her crew, and some unexpected allies fight to avert destruction on a planetary scale. Meanwhile Lieutenant Nog and Ensign Thirishar ch'Thane search for a way to shut down the portals forever; and behind the scenes Quark plays a dangerous game that could determine, once and for all, who wins control of the Gateways...
________________________
It has been a long time since I read this one, but I remember that I really liked it. Good continuation of the ongoing stories in the DS9 series, one of the stronger entries in the Gateways series and of course the set-up for a very, very strong short story in the seventh Gateways book.