Krenim weapon ship
In several alternate timelines, the Krenim weapon ship was a warship of the Krenim Imperium capable of erasing civilizations from history. Its design and construction was spearheaded by Annorax, a military temporal scientist.

History

Deployment 
The design of a weapon that pushed targets out of the space-time continuum, and the construction of a ship to house it, was overseen by Annorax in the 22nd century. In the 2170s, the weapon ship was activated and used against the Rilnar, the primary enemy of the Krenim Imperium at the time. This temporal incursion restored the preeminence of the Krenim, but unexpectedly also resulted in a plague that cost over fifty million Krenim lives. Annorax attempted to rectify his error with a second incursion, but inadvertently erased the Krenim colony at Kyana Prime and with it his beloved wife.

Annorax continued to alter history with the weapon ship over the next two centuries, obsessed with restoring his wife. Among the civilizations he eliminated were the Alsuran Empire, the Malkoth, the Zahl, the Garenor, and the Ram Izad.

Use against Voyager 

The weapon ship was also employed against the Federation starship  (Component 049 Beta in their calculations). Voyager had been passing through what in a previous timeline had been Zahl space when Annorax used the weapon to erase the Zahl, turning Zahl space into Krenim space. Attacked repeatedly by Krenim warships using chroniton torpedoes against which their deflector shields were useless, they were forced to develop temporal shields to use against the torpedoes. These shields disrupted the precise calculations Annorax' crew had made to direct the results of their temporal incursion against the Garenor. This caused the incursion to "miss"; instead of the desired results, that is, the restoration of all of Krenim territory, including Kyana Prime, a timeline was created in which the Krenim Imperium never existed at all. This was, of course, totally unacceptable, and thus Annorax turned the weapon on Voyager. Voyager, however, was able to escape by going to warp speed, taking advantage of its faster warp capability to outrun the weapon ship.

Self-erasure 

The weapon ship itself was eventually erased from history when Voyager, all but destroyed by Krenim attacks, led a small fleet, composed of two Mawasi cruisers and three Nihydron warships, against it. Tired of the seemingly endless and futile mission, some of the crew, led by Annorax' second in command, Obrist, shut down the temporal core. This caused the ship to phase back into normal space time, so that conventional weapons could affect it. Though the vessel's conventional weapons were limited, they were still enough to overpower the attackers. 

However, Voyagers captain, Kathryn Janeway, was aware of the exact location of the ship's temporal core. Alone on her ship after being forced to order the rest of her crew to abandon ship due to its ruined state, she piloted it into that section in a ramming attack, causing the core to destabilize. This exploded the weapon ship and, moreover, caused a temporal incursion that erased the ship itself from history, and with it, every one of the alterations in the timeline it had ever made. 

Ironically, this had the effect of accomplishing exactly that which Annorax had been attempting to do for centuries; Kyana Prime was restored, and as was Annorax's wife. ()

Key events 

For the events from the perspective of Voyager, see Year of Hell.
Annorax constructs the ship. His first action is to turn it against the Krenim Imperium's greatest enemy, the Rilnar. Once the Rilnar are gone from history, in an instant the Krenim are restored to their former power. However, a rare disease breaks out among Krenim colonies and within a year fifty million are dead. Annorax has failed to realize that the Rilnar introduced a crucial antibody into the Krenim genome. 
In the ship's second action, the Krenim colony at Kyana Prime, and with it Annorax's wife, is unexpectedly lost. For the next two centuries, the ship tries to undo the damage. Thousands of worlds and billions of lives are removed, brought back, and removed again. While the crew remains focused on restoration of the Imperium, Annorax becomes obsessed when Kyana Prime remains elusive.
2374: Voyager avoids a rogue comet, component 37329, which Chakotay later determines is the action that led it to entering Krenim space.

The ship erases a Zahl colony, but fails to achieve the objective of that action. Annorax orders a course set to the Zahl homeworld, with the goal of erasing the entire species.
 enters Grid 005. They find that the Zahl are its primary species after defeating the Krenim Empire, which previously dominated the space, a generation ago. The planets they annexed retaken and their military forces dismantled, low warp Krenim ships with limited armaments harmlessly wander the area, harassing passersby with grandiose claims that the territory is still disputed.
Annorax targets the Zahl homeworld and erases the Zahl species. This results in a 98% restoration of the Krenim Imperium, 849 inhabited worlds spanning five thousand parsecs. This is the best outcome in two hundred years of work and much of the crew advocate calling it a day. However, the Imperium still does not extend as far as Kyana Prime, and given that the crew has all of eternity, Annorax insists on trying for yet a better outcome. Voyager suddenly finds itself already within the Imperium (though is not aware of the change), and in the following weeks sustains serious damage in continuous Krenim attacks.
Sixty-five days after the Zahl colony erasure, Voyager manages to implement temporal shielding, which makes it unaffected by the changes in the timeline caused by the Krenim weapon ship. 
Annorax targets the Garenor homeworld to erase the Garenor species, an action which backfires as the Krenim Imperium reverts to a pre-warp state. Protected by its temporal shielding, Voyager detects the disappearance of Krenim colonies in its vicinity, as well as the Imperium's reduction from two hundred star systems, nine hundred planets, and thousands of warp-capable ships to to a few planets and a smattering of vessels. This is the first time Voyager is aware of the changes in the timeline.
Seventy days after the Zahl colony erasure, in the wake of the Garenor fiasco, Annorax identifies Voyager as a problematic element in his calculations, and Voyager identifies the weapon ship as the source of the anomalies. Annorax takes samples of Voyager, which includes the capture of Tom Paris and Chakotay.
Around 207 days after the Zahl colony erasure, the ship erases Ram Izad, resulting in a 52% restoration. Kyana Prime is not restored.
Two hundred fifty-seven days after the Zahl colony erasure: Voyager leads a fleet of six ships representing two other powers, the Mawasi and the Nihydron, in an attack against the ship. It is destroyed. This changes the timeline so that an oblivious Annorax appears to live with his wife again. Upon entering Krenim space, Voyager is warned by a Krenim ship that the area is in dispute, and plots a course around.

Technical data

Method of operation 
Its main weapon was a beam that pushed objects out of the spacetime continuum, effectively erasing them from history. Careful and meticulous calculations were required to create the exact changes in the timeline that were desired. The ship could be deployed against an entire species by firing the weapon on the species' homeworld, pushing the species out of the spacetime continuum. This caused a causality paradox; all of history the species played any part in would be altered. 

The following gallery is an illustration of the method of operation, in which the weapon was used against a colony.

Capabilities and limitations 
The ship obtained its power to affect time from its temporal core. When in operation, the core also kept the ship, and everything and everyone on it, outside of normal space-time. This rendered the ship immune to all conventional weapons and protected the crew from the flow of time, effectively rendering them immortal. Without the temporal core however, the ship was vulnerable as its shields were so weak that even a photon grenade could penetrate its hull. In addition, the vessel's great mass prevented it from exceeding warp 6. The ship did mount a formidable array of directed-energy weapons for conventional warfare. ()

Appendices

Apocrypha
According to Star Trek: Attack Wing, this ship is named the Kyana Prime.

The Star Trek Online mission "Time in a Bottle" reveals that the Krenim are aware of the events that befell Annorax, and offer the Delta Alliance (the Federation, the Klingon Empire, and the Romulan Republic) a set of schematics for the weapon ship to be used against the Iconians; in "Broken Circle", the Alliance makes an attack against the Iconians to give the researchers time to complete the ship. In the mission "Butterfly", the ship – christened KIV Annorax – is completed, but the researchers reveal that using the weapon directly against the Iconians would result in the discovery of warp travel being delayed for more than fifty thousand years. After holodeck simulations to determine an ideal scenario, the ship makes a temporal incursion that restores the destroyed planet of Romulus, but finds it has been completely assimilated by the Borg. The ship is thus forced to make another temporal incursion, this time against the Borg transwarp network; the ship is damaged by Borg attacks and its temporal shielding fails, reintegrating the ships and their crews into the "main" timeline. The Annorax also plays a major part in "Midnight", the final mission of the Iconian War storyline, opening a portal to allow the player character to go back in time and somehow stop the Iconians.

In the Future Proof storyline, tying into the Agents of Yesterday expansion, the Krenim lead researcher Noye hijacks the Annorax, allies with the Na'kuhl, the Vorgons, and the Sphere-Builders, and attacks the signing of the Temporal Accord. He later augments the ship with Sphere-Builder technology. In "Ragnarok", the final mission of the storyline, Noye commands the Annorax at the Battle of Procyon V; after the Sphere-Builders' spheres are destroyed, the player disables the Annorax, boards the ship to disable its temporal core, and captures Noye.

The ship was later made available to players as the "Annorax Science Dreadnought".

External link

de:Zeitwaffenschiff

Krenim starship classes
Time travel technology