Star Trek Deep Space Nine: The Soul Key by Olivia Woods
The DS9 relaunch books began in 2001 and TPTB are really, really dragging the plot out ever since 'Unity'. This book is all about the mirror universe. Why are TPTB clogging up the DS9 books with mirror universe tales when the mirror universe have their own book series? TPTB have been hinting at this coming big enemy, the Ascendants, for literally years now and nothing has come of it.
The DS9 books are running in place. This novel was a boring waste of time that did nothing to advance the plot. It's a useless side story. The DS9 books are running on empty. Kill it before it dies or do something, anything to fix things.