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Fan Fic / Catalyst EXE

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Catalyst.EXE is a Mass Effect Self-Insert by Shujin, which details the life of a doctor named Rebecca who wakes up on Ilos, trapped within the memory banks of a Prothean computer. After adjusting to her new situation and creating an android body for herself, she sets about to preventing the canonical plot by doing her best to fortify Ilos, and prevent Saren from utilizing the Conduit to sneak Sovereign into the Citadel.


To this end, she creates two Prothean V.I. to help protect Ilos and defend it against Saren. Aegis, a dependable, solid administrator, and Veto, who is designed to do one thing and one thing only: destroy as much of Saren's army as possible, while denying him the use of the Conduit.

Unfortunately, while [Rebecca] is busying preparing for the invasion of Ilos, Commander Shepard and his noble team of soldiers are off trying to prevent the apocalypse, under the guidance of his Spectre mentor, Saren, and accompanied by veteran asari Matriarch, Benezia. Even more unfortunately, when [Rebecca] finally leaves Ilos, she has not realized that this world is not the same as the videogame of her memories, and leaves Veto in charge of the fully armed and operational facility.

What follows is a story focused on the depth of emotions, the difficulties of being an artificial life, and why networking everything is a horrible idea.


Hosted originally on Spacebattles, it is also hosted on Sufficient Velocity, and

Beware, major story spoilers below!

This fic contains examples of:

  • Adaptational Heroism: Saren and Benezia didn't get indoctrinated, and are actually members of Shepard's squad, though Saren is apparently nominally in charge as Shepard's mentor.
  • Adaptational Villainy: It appears that Nihlus was indoctrinated in place of Saren, and died on Virmire in a nuclear explosion.
  • Ascended Extra: Virgil, who canonically 'dies' short after his introduction.
  • Big Bad: Inverted. It turns out that [Rebecca] is the Big Bad of this story, due to being an altered version of the Catalyst designed to fix the failures that the original Catalyst created: the Reapers themselves. Up until she dies at the end of the invasion of the Citadel, that is. She got better.
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  • Big Damn Heroes: In the Battle of the Citadel, the Normandy arrives just in time with an army of non-heretic Geth.
  • Death Course: Ilos, after [Rebecca] and Veto fortify it to prevent Saren from accessing the Conduit. While it succeeds in preventing both the Heretic Geth and Shepard's team (with Saren in it) from doing so, the fortifications change Ilos from a decrepit ruin into a cross between Aperture Labs and the Tomb of Horrors.
  • Everything Is Online: When [Rebecca] takes control of the Citadel, she is bewildered that she can hack everything, from security systems to weapons to a toothbrush.
  • Flat "What": Saren, upon hearing that Veto is still alive after the Normandy had bombed its facility into rubble.
  • Genghis Gambit: [Rebecca] pulls one on the Citadel, masquerading as an evil A.I. in order to teach them to stop networking all their computers together and prepare them for Sovereign's invasion. Unfortunately, Sovereign notices that all of the Citadel's defenses are down, and decides that it is the perfect opportunity to invade.
  • Hero of Another Story: Due to Commander Shepard having Saren as his Spectre mentor, he never has a reason to recruit Garrus, as Saren is capable of filling his role in the squad with his experience and knowledge of technology. When the invasion of the Citadel kicks off, Garrus takes charge of the C-Sec HQ and rushes to acquire non-networked firearms.
  • Heroic Comedic Sociopath: Veto, full stop. As a V.I. designed solely to control defensive fortifications against an invading army, Veto lacks many of the basic functions of other V.I. It will gladly interrupt whenever it feels like it, delights in causing explosions and destruction, and at one point starts counting points out loud for [Rebecca]'s kills, much to her irritation.
  • Ignored Expert: Zig-zagged with Tali'Zorah, who warns C-Sec and the Citadel of the incoming threat to Council Space. While she is taken seriously, her warnings about the folly of making your guns capable of networking with other systems is ignored. Garrus is the only one who takes her seriously, and even then, only after the invasion of the Citadel kicks off, when he realizes that she was right the whole time.
  • Insistent Terminology: Due to [Rebecca]'s nature as an A.I. controlling an android body, her thoughts (and much of the prose) are framed as input/output between computers, and her name is always surrounded by single brackets, as indicated on this page.
  • Noodle Incident: Saren has saved Shepard's life five times, including dealing with a drell assassin. One incident apparently included asari commandos and "that one drugged Hanar on Illium"
    "Yes, yes," Saren waved an impatient hand... In his defense, losing a trainee to that mess would have been an embarrassment.
  • Red Eyes, Take Warning: Veto's avatar is a single glowing eye. The mere sight of it freaks Miranda Lawson out, after the first time she met it.
  • Robot Girl: [Rebecca] use a gynoid body to interact with the physical world.
  • Running Gag: [Rebecca]'s A.I. brain often informs her of the emotions that she is feeling, and asks if she wishes to disable them.
    Fear detected. Disable? Katrina
  • The Dreaded: To Shepard, Saren, Benezia, and the rest of his crew: Veto. Shepard, a hardened war hero, goes ballistic upon seeing that even calling in the Normandy to bomb the facility on Ilos had not been enough to kill it. Saren, upon hearing the news, immediately wonders what it would take to finally kill it. He decides that a big enough nuclear bomb would do the trick, and that if even that didn't work, that he'd just attach engines to the planet and ram it into the sun.
    The AI, Veto, dropped in on the call.
    "Still alive?
    Shepard went berserk. "We fucking killed you –"
  • Think Nothing of It: Zigzagged. Shepard got a medal after the Skyllian Blitz, and he doesn't even know where it is. He also got a couple dozen letters from children that he saved from slavery. He framed each and every one.
  • Weirdness Censor: [Rebecca]'s core is made from parts of a Reaper, and she can't see or realize this. It takes [Ana]'s discovery of this truth and her subsequent fleeing of the system for [Rebecca] to break the censor and look at her own core.

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