Mona Sax

 First Appearance 

When both Solaris and Ebrown had been investigating the facility that Alliance scientists had held down in, everyone was already dead inside, consisting of only Cerberus troops. Both commanders were suspicious, only the work of a skilled assassin could have carried out such a plot to infiltrate and kill everyone in the facility.

When observing over Prothean files, information from the console was missing. Seconds after the message the door was kicked open by Mona, who held both commanders at gunpoint. Mona claimed she had the usb with the information on it and she was going to betray Cerberus to get what she needed from them, and use it to her advantage to possibly save the galaxy, or help save the galaxy, on her own. Mona said goodbye to both commanders and shut the door quickly, locking it. Before Mona could escape, Bullet who was around the corner listening, ambushed and tackled Mona, taking the USB. Bullet was heard saying she was going to report Mona and say that she tried to betray Cerberus, and that she was already out of the faction. Mona didn't call out for help, only cursing back at Bullet. Bullet claimed that she was going to kill Mona, putting a gun to her head and about to pull the trigger. Before she could press it, the door holding Ebrown and Solaris exploded, and before they could apprehend Bullet she shot Mona in the chest and took off with the USB. Solaris and Ebrown looked at Mona, who yelled at them to go chase Bullet since she had the data.

Both commanders chased down Bullet, who was crossing over broken ice to get to a Cerberus gunship waiting on the other side. When both commanders got to the other side, Bullet already entered the gunship that was prepped for takeoff beforehand, launching into the sky. Both commanders fired RPG's at it and watched it crash not soon after it took off. Ebrown told Solaris to search the rubble for whatever was left while he went back to tend to Mona. Bullet soon crawled out of the debris and looked at the USB drive that fell from the crashed gunship, another gunship roared above Solaris, although it was only trying to save Bullet, who chose to save her own life and escape rather than fight for the USB. Solaris recovered the USB while Bullet escaped and returned to Ebrown who tried to help Mona, who was telling them to leave her and not help, she said she had no feelings for them anymore and Ebrown prompted her to shoot him, she picked up the gun and aimed at him, trying to say "Sorry" before she passed out, not able to shoot him. She then went into shock, forcing the commanders to do all they could and call for an evac, who was already waiting for them. Young waited outside the shuttle, taking Mona while they got in, he congratulated their victory, explaining that he suspected Mona was behind the facility infiltration.

Mona was transported back to the ship and cared for under the ships medical facility, she was constantly scanned for internal bleeding and infections, and then had surgery to fix her wounds. Mona recovered soon after, and was confronted by both commanders. They prompted her to join them again but Mona said she didn't want to, she didn't want to be a "family" because it's not what she is supposed to do. She claimed that there is no family since everyone is dead, and Ebrown said that wasn't true since some of the family is on the ship. He continued to bring up Raiden which enraged Mona, she yelled at him and apologized soon after, saying she didn't know what to do. Ebrown and Solaris told her that they needed all the help they could get, wanting her to join on the mission. She told them to talk to her later and she'll make up her mind.

 Betrayal 

Both commanders passed Mona a few days later, she claimed she made up her mind and wanted to go back to The Citadel and carry out whatever was waiting for her. The commanders asked her if she was sure, saying they still wanted her. She then claimed they lost a lot of people on the suicide mission and she couldn't fear losing anymore people because she isn't supposed to fear anything at all. Mona was accepted a ride back to The Citadel, and dropped off two folders before leaving. Soon discovered, one folder held very confident information. Young observed the data and zoomed into a picture, which revealed The Ulyssey with Cerberus scientists and troops on it, repairing it and ready to launch it into space again. Mona had a voice recording waiting, which played "Now you know about my plan, I'm going to take that ship back and keep it for what it was meant to be, I'll see you there commanders, and this will be the last time"

Mona was holding up in the debrief room, which was right next to Raidens room. She held Alyssa at gunpoint and exclaimed that if either commanders tried moving a step near her, she'd shoot her. She prompted that she'd shoot her over and over until she told the commanders to shut up, and saying she'd give the commanders Alyssa if they left her alone. Solaris and Ebrown both agreed and said they had what they needed, Ebrown tried convincing Mona to destroy the information but she declined, saying she wanted to keep it all because its all she had left. Before giving Alyssa back, she claimed that neither were going to leave alive because she knew they'd come back, she opened Alyssa's jacket and had c4 strapped to her with a timer, rolling her down the stairs. Solaris stayed to help Alyssa while Mona and Ebrown fought through the ships cargo deck. By the time Solaris got the c4 off Mona came back to the room and told him that he did a good job, and "nice try" getting ready to shoot Alyssa in the head with her AR2. Both commanders prompted her not to, and shot her before her finger slid the trigger down.

Mona lay dying in a pool of blood, exclaiming that she'd kill both commanders and get her revenge, and that they only hurt her. Ebrown and Solaris felt bad for Mona, trying to still convince her to not try and kill them and just let them leave and help her. Mona reached for the gun she had dropped on the floor, saying that she had enough with Ebrown. Before she could pick up the gun, Ebrown and Solaris both said goodbyes to Mona, ending with Ebrown shooting her in the head, leaving the room right afterwards.

Ebrown was convinced that Mona now found her happiness, forever at peace with herself and possibly finding Raiden on the other side, a question he often asked himself about Janice and Harris.