Marathon: Red Shift is a Mass Effect and Marathon crossover by CrazyEyedMustafa.

Serin Shepard is unwell. Between the stress of her mission and the existential questions raised by her resurrection, this would be understandable in and of itself. But she's been having strange dreams lately. Dreams where she's running from something behind her, and can never quite escape. Dreams where a voice on a computer screen talks to her, and she can never quite remember what it says.

Meanwhile, on Omega, a down-on-his-luck quarian, while digging through the trash for scraps to repurpose and sell, stumbles upon a human buried in the refuse. Horrifically injured, but somehow still alive. Against all his better judgment, the quarian drags the human home and does his best to help him.

Little does he know, this human is far more than he seems.

Also available on Spacebattles.

Marathon: Red Shift contains examples of the following tropes:

• Ascended Extra: Kenn the quarian was only involved in one sidequest in Mass Effect 2, and is not mentioned in any of the series' later entries, regardless of how you resolve it. Here, he becomes a major supporting character for Roland.
• Adaptational Villainy: Downplayed as he's still a sympathetic character, but Kenn never expressed a willingness to commit murder to get out from under Harrot's thumb in canon.
• Because You Were Nice to Me: Roland ultimately befriends Kenn because the quarian was the first person for as long as Roland can remember to show him genuine kindness without any expectation of reward.
• Boom, Headshot!: Roland is on the recieving end of one of these, courtesy of Garrus. Then the chapter ends.
• Crossover Power Acquisition: As part of the Fusion Fic: It's all-but stated that Shepard was rebuilt by Project Lazarus with Jjaro implants, enabling her to travel through parallel timelines.
• Death by Adaptation: Roland murders Harrot the elcor merchant at Kenn's request, so the quarian can take over his business.
• Didn't Think This Through: Kenn knew that Harrot had connections to the Blue Suns, but never considered that they would connect their best merchant being murdered to the quarian who stepped in to take over his business so quickly.
• Dies Differently in Adaptation: In canon, Morinth is either killed by Samara and Shepard in Mass Effect 2, or turned into a Banshee by the Reapers and put down by Shepard in Mass Effect 3. Here, she gets her head crushed to paste by Roland after trying to Mind Meld with him, just days before Shepard and Samara came to track her down.
• Dreaming Of Things Gone By: Commander Shepard occasionally has dreams where she relives the memories of Roland's childhood on Mars, much to her confusion.
• Fantastic Racism: Countless years (from his perspective) of fighting the Pfor have left Roland... touchy regarding aliens. Especially quarians, since both species have three fingers on each hand.
• Fish Out of Water: Roland/Security Officer is decidedly out of place in the universe of Mass Effect, as he is not used to interacting with sapient alien species' that exhibit human-like behaviors; in Marathon, the majority of non-humans encountered are hostile and impossible to communicate with, or lack the faculties for intelligent thought.
• Healing Factor: After fighting Morinth, Roland is left missing part of his brain and half of his tongue. A day later, both have grown back almost completely.
• Lean and Mean: Roland's physique is described as thin, bordering on emaciated, and his personality can charitably be described as... prickly.
• Made of Iron: Roland. He slaughters an entire warehouse of Blue Suns mercenaries with no armor or shields, taking literally hundreds of bullets and, at one point, a shotgun blast point-blank to the face, and barely slows down throughout all of it. He even survives a Mind Meld with Morinth, something not even Shepard could do in canon.
• Major Injury Underreaction: While Roland and Kenn are trying to catch a ship off of Omega, Roland gets shot In the Back. Roland barely flinches, turns around and snatches the gun out of the shooter's hands, and tells her not to do it again.
• Meatgrinder Surgery: At some point before arriving in the Mass Effect universe, Roland nailed his chestplate to his own torso, forcing Kenn to remove the nails with a claw hammer and a pair of pliers when they have to get Roland out of his armor.
• Missed Him by That Much: Roland and Shepard miss each other several times on Omega.
• Mundane Luxury: Roland reacts to the simple bowl of soup Kenn buys him like it's the best thing he's ever eaten. He initially assumes the quarian is trying to bribe him for something.
• Named by the Adaptation: Zig-Zagged, as Roland is one of many names the Security Officer has had (whatever that means).
• No One Could Survive That!: During Samara's fight with Roland, she notes that even the most advanced combat synthetic would be reduced to powder by the sheer kinetic force she's throwing around. Not only does Roland keep getting up, he doesn't even slow down.
• Plotline Crossover: Shepard and Roland experience their own plots divorced from each other for much of the story until they cross paths due to both having a mutual connection to Morinth, and by extension, Samara.
• Power Incontinence: During a shore leave with the rest of the Normandy's crew, Shepard's Jjaro implants start going off at random, catapulting her through wildly different timelines, much to her disorientation and confusion.
• Strong Family Resemblance: Samara looks nearly identical to her daughter, Morinth. This ends up biting her hard when Roland mistakes her for her daughter and attacks her.
• You Are a Credit to Your Race: Roland is in the uniquely awkward position of not caring one bit for non-human sapients (to the point of regarding one human-turian couple he encounters with utter disgust - almost akin to bestiality), whilst and at the same time considering Kenn the Quarian his Only Friend.
• You Didn't Ask: This is Miranda's excuse for why she didn't give Shepard more information about the combat synthetic (Roland) Cerberus was trying to buy from the Blue Suns. Shepard is not amused.
• Your Head A-Splode: How Morinth meets her end, courtesy of Roland's fist.