You've kept this dark purple crystal that you stole from a Circle lair. Although its colour has darkened and you no longer feel any power within it, it's a potent reminder of the adventure you like to think of as:
Breaking the Cage
It began with an insidious plan. Crash Cage wanted to feed the Circle intel on some Cage higher ups, but she knew she'd be the first suspect when things began to go wrong in her father's company. So she sent you to a patsy, Vince Dubrowski. Vince was unfailingly loyal to Cage Consortium, but he had a crush on Crash, so she was able to manipulate him into giving up the name of the company's CEO: Leonard Sykes. You kidnapped the unfortunate Mr. Sykes, despite the best efforts of Cage security.
You went to deliver Sykes' location to the Circle, but the Legacy Chain was waiting for you. You defeated them and managed to get the information to the Circle representatives on the scene. When you returned to Crash, however, her speech was strange. Something had clearly happened during your absence.
Crash advised you to go to a Circle lair where you would 'meet your destiny', but something about the situation seemed fishy. Instead, you went to Vince Dubrowski, to see if he had any insight into Crash's strange behavior. He told you he had been warned against just such an event. He wanted you to retrieve a Circle crystal that would restore Crash to her old self. You did so, and in the process came face to face with Leonard Sykes for the second time. The wimpy executive had undergone quite a transformation, setting himself up as a Circle of Thorns mystic. Once you secured the crystal, you took it back to Crash, who became her old self once again. She said that the Circle had decided to change her once they learned that she was unwilling to return to Cage Consortium and help them cement their control.
In the end, Crash was happy to have done so much damage to her father's company. You, of course, were happy to get paid.