Please note that this souvenir is for failing the story arc. Please see "Valkyrie's Shoulderguard" for the successful version.
There are a lot of strange things to know about the Rikti, but you've learned one of the strangest. That not all of them are aliens. And that the one you're working for used to be a villain named 'Corey'. All this is and more comes back as you hold a piece of Positron's armor and remember the time you helped cause:
When Ambassador Kuhr'Rekt told you he felt he could trust you with an important task, you really didn't expect him to start talking like a human, or to reveal that not only was he once a human named Corey Ekter, but that he used to be the famous nuclear terrorist known as 'The Corrector'. Corey, er, Kuhr'Rekt explained that since he used to be a fellow villain before he joined the Rikti and was transformed, he felt that you could understand a need for revenge he still felt, a need for revenge that he had kept quiet from his fellow Rikti. The first part of his revenge was to have you kidnap a friend of one of his targets, a Dr. Oscar Westway.
With Dr. Westway in captivity, Kuhr'Rekt told you a bit more about how he'd gotten into a job that went wrong, and been labeled a nuclear terrorist, had his armor destroyed, and was drinking himself into an early grave when the Rikti attacked. But soon enough it was time to continue the battle, and the next step was a big one. Kuhr'Rekt had placed false leads about Dr. Westway's location to draw out his first target, none other than Positron himself! But Positron wasn't even the real target.
When Kuhr'Rekt revealed his true target, you were kind of puzzled to learn that he wasn't even after Positron but Valkyrie, Positron's sidekick. It turns out she was the one who defeated him and ruined his armor years ago. Of course, the defeat is what led him into the Lost, and through them the transformation into one of the Rikti and the high standing he has today. Some people just can't let go of a grudge, but he is the one paying the bills and the fight sounded interesting, so in you went. With an enraged Valkyrie, an angry Positron, Longbow troops, and a 90 minute time limit to contend with, it wasn't going to be easy.
In the end, you weren't quite able to pull it off. Valkyrie got away and took Positron with her back to Paragon City. Kuhr'Rekt was upset, but seemed to take it in stride. That, or he'd just gotten better at repressing his human side. Still, he did pay you even if he didn't get his revenge. Maybe the Rikti aren't that bad after all, but you're still rather not be one. After all, how advanced could they be if they didn't understand the elementary desire for revenge?