Unnecessarily Evil Initiative Omega-91 was one of a number of initiatives in Dr. Nefarious' stratagem. While the exact details of the procedure were unknown, it was activated to entrap Alister Azimuth and Ratchet so that they could no longer interfere with the doctor's ultimate goal to control time by taking over the Great Clock.
After Lawrence had notified Dr. Nefarious of his capture of the Great Clock's Senior Caretaker, Clank, Nefarious ordered the Valkyries to enact the initiative on planet Vapedia; Clank was to be used as bait for Ratchet and General Azimuth. Upon entering the Bernilius Sector from coordinates stolen from Lord Vorselon, Ratchets' starship, the Aphelion, detected a distress call with Clank's signature coming from Vapedia. As Ratchet headed towards the planet, he was ambushed by Carina and her squad of Valkyrie fighters. Defeating and killing her in space combat, Ratchet allowed himself and Azimuth to land on Vapedia, unaware that they were walking straight into an ambush headed by the waiting Cassiopeia.
The ambush and events caused by the initiative were part of implementing Unnecessarily Evil Initiative Omega-96, not Unnecessarily Evil Initiative Omega-91, as Cassiopeia had failed to read a memo from Dr. Nefarious causing her to active the wrong initiative.
After gaining access to the Valkyrie Citadel, Ratchet and General Azimuth were met by Cassiopeia and Valkyrie troops. Initially, Azimuth pursued Cassy when she departed to kill Clank. Simultaneously, Ratchet fought the teams of Valkyrie warriors sent after him throughout the citadel. He eventually headed straight into their training course. It was here that Cassy confronted the Lombax again, having evaded Alister Azimuth.
As Ratchet escaped the various deathtraps and General Azimuth fought additional waves of troops, both searching for Clank all the while, Dr. Nefarious and Cassiopeia were heard over loudspeakers arguing over how Ratchet was not being attacked and dealt with the way the doctor had instructed. After Ratchet survived the death course and Azimuth eluded the Valkyrie troops, Cassy revealed Clank's location in her quarters, ready for a duel with Ratchet. She was defeated and after nearly two years separated Ratchet and Clank reunited.
All attempts to contact your lady friend have been unsuccessful. Perhaps she thought about marrying you and decided to make a run for it?Lawrence updates the disguised Ratchet on the failure of the initiative., ACiT
After the defeat of the Valkyries, Ratchet and Clank infiltrated the Nefarious Space Station with the aid of the undercover Captain Qwark. Using a Dr. Nefarious holo-guise, Ratchet discovered that Lawrence was unable to contact Cassiopeia after the mistaken initiative's failure.