The so-called "Death Stars" were under the general command of a cohort of Future Guy, hoping to alter the outcome of the Dominion War as part of the Temporal Cold War. The major limitation of the "Death Star" was that it could only exist in its past for a very limited amount of time. The time travel ability was based on a principle of folded space transport. (Star Trek: Lambda Paz: " The Tides of War, Part 1")
- That such direct actions were not taken to alter the 22nd century suggests that this approach to time travel does not stretch that far back.
These ships were first encountered in the 24th century in 2374, during the First Betreka Nebula counterstrike of the Dominion War. Two them appeared and opened fire on the USS Lambda Paz. These ships torpedoes were capable of penetrating Starfleet defensive shielding. Their strategy was to slow the ship down and allow two nearby Jem'Hadar fighters to come around for another pass. The Jem'Hadar then boarded the Lambda Paz and the ensuing firefight led to the death of MACO commander Jonathan Davis.
The "Death Stars" were encountered a second time by 24th century Starfleet personnel, after Captain Limis Vircona and Ensign Rebecca Sullivan of the Lambda Paz escaped the custody of Sindareen proxy agents. This time, however, a time traveler from the 31st Century made modifications to the runabout USS Potomac's weapons and shields.
During a third encounter, Captain Limis ordered tactical officer Jovis Ren to unseal a computer file on Grabowski's modifications. In anticipation of the time traveling ship's strategy, Limis then ordered the Lambda Paz out of warp to disable a Galor-class Cardassian warship dispatched by Gul Hadar to capture Limis. (Star Trek: Lambda Paz: " The Tides of War, Part 1")