When trying to avenge the death of their leader Cave Jonson, the evil TEEN FORTRESS 2 at first considered writing mean things on Marrissa's Facebook; unfortunately, this failed as Facebook didn't exist at the time. As such, the evil TEEN FORTRESS 2 created an evil clone of Marrissa, who called herself Assirram Strebor. Before she could go on her mission, however, the evil TEEN FORTRESS 2 put Assirram's evil to a test. She corrupted the robot which became known as GLaDOS, in Portal High School, found the needle which gave her speshul powers and set off to the future. During her brief time, she quickly becomes rogue, not considering herself affiliated with her creators, even going so far as to kill them.
In the future, Assirram commands the zombie army from Andord Hell, aiming to take over the world. However, Marrissa appears at the right time, defeating the zombie army's biggest zombie, The Ultimate Zombee. Marrissa and Assirram thus call each other to a "portal battle", which takes them to the time of the dinosaurs, the Death Star (where she briefly poses as Dark Vader) and Portal High School. Ultimately, Marrissa wins the portal battle, killing Assirram. Her zombie army was taken care of by the good TEEN FORTRESS 2.