The Battle of Rigel was an engagement between Federation Alliance and Dominion forces in the Rigel system, which took place in early 2375. The Federation Alliance successfully repelled a Dominion attack on long-standing Federation member system, the United Rigel Colonies.
The USS Kelly was among the vessels lost in this engagement. In the aftermath of the battle, the Orion Syndicate sent ships into the debris field to scavenge whatever they could before Starfleet could recover its own technology. One such item was an isolation suit from the USS Kelly, which eventually found its way through the black market to Hiziki Gard. (DS9 novel: Trill: Unjoined)