A.N. If you want more information about something than context clues provide, check out the Codex section at the bottom. Like in the Mass Effect video games, the Codex contains optional explanations of technology and other elements of the setting. If you don't understand what a sentence is talking about, or are confused by something that doesn't fit with lore from the original Mass Effect, the Codex can help. Also, while many canon events and conversations will take place, I will usually only go into detail when things are different from canon.

Theme Music: Arrival

Eden Prime burned. Where once verdant pastures and waving fields of corn and wheat stretched as far as the eye could see, ash and shadow blanketed the land in a shroud fit for the desiccated bodies concealed beneath the choking grit. Perhaps farther away from the colony, the rest of the planet remained untouched, but if anyone, anything still lived near the pride of the Systems Alliance, they would be unable to tell. And if they lived, they would be wise to keep their heads down.

Hovering over the blasted ruins lay the source of this disaster, a great, black starship, twisted devices extending outward from its core like the grasping fingers of a malevolent hand. Lancing from the glow at the 'palm' of the monstrosity, a crimson beam of pure energy promised death to those who had the misfortune to come to the great leviathan's attention. A deep, pulsing thrum emanated from the center of the mass of dark metal and bright death, pitched to grate in the bones of any listeners… if anyone was still alive. Yet, it seemed that someone was.

Three figures crested a low hill to the east, silhouetted in the dying light of the day, as though Eden Prime itself paid its respects to the catastrophe it had witnessed. Each figure wore nigh-identical sleek, dark armor largely free of adornment, though slight differences made each figure distinct. The lead figure, unlike her flankers, was clearly female, a small glyph on her breast proudly proclaiming her status? rank? as "N7". She cradled a stubby firearm in her arms, helmet angled to keep both the massive ship and the ground in view.

The leftmost figure stared blankly at the looming thing in the sky, a long, slender weapon held loosely in his right hand. His mouth, the only part their armor left visible, worked a few times, as though he could barely comprehend what he saw.

The rightmost figure carried the smallest weapon of all, but in an easy, comfortable grip. His left hand, enveloped in a corona of orange symbols and geometric patterns, extended toward the leviathan with the air of a tourist making memories with a camera phone, but the set of his jaw, the way he moved, suggested that this man would remember the deadly ship for very different purposes… and that its captain, whoever that might be, had just made the top of a list that no sane person wants to be on.

"Wha- What the hell is that thing?" the leftmost figure gasped, "Did it do all this? And how do we kill it?"

"Us? Against that?" the man on the right questioned, giving the impression he was quirking an eyebrow, "I want my pound of flesh as much as the next man, but I don't fancy the chances of three ground-pounders against a full dreadnought. Pick your battles, private, and be thankful that we're probably too small for the opposition to notice. Unless you do something stupid, so pull yourself together. Save the rage for a target your gun's actually gonna hurt."

"Then you're both in luck, Alenko, Jenkins," the woman informed them, pausing briefly to log something on the ground with an orange, glowing device of her own, "Tracks. Don't match anything in the database. The thing's got ground troops, and they're probably after the same thing we are. The only thing worth attacking Eden Prime for is something political, or the Prothean beacon. And if this was politics, we'd be seeing Batarians in the skies, or maybe Turians, not… whatever that is. So we need to secure the beacon, and fast. Caution isn't a priority anymore. On the double, people! Jenkins, take point."

Jenkins, now identified as the man with the largest gun, shifted his weapon into a more alert position and proceeded to the van, eyes sweeping over the area as he jogged forward. The woman took her place behind him, weapon ready, and Kaiden took the rear, each soldier covering the others' blind spots as best they could. However, before they could move ten steps, three hovering machines swept into the area with a loud buzzing and opened fire, prompting the team to take defensive action.

Jenkins displayed impressive reflexes, diving for cover with a microbooster-assisted dash. Though he was still clipped by a few shots, swift action and a scintillating shield of energy kept him from serious injury. Kaiden shrouded himself in a thick barrier of energy with a quick gesture, like Jenkins' protection put on overdrive, bullets bouncing harmlessly off the gravatic shield as he calmly directed a stream of pistol fire at the farthest enemy. Experience told him that the nearer ones wouldn't be a problem for long.

When a streak of screaming blue flew past him, Kaiden knew he wasn't going to be disappointed. Propelled by boosters and an aura of azure power, the N7 slammed shoulder first into the nearest drone, crumpling the murderous machine like a tin can, and opened fire with her weapon on the closest functioning target, shotgun spraying the area with shards of metal. Understandably, both drones focused on this obvious threat, giving Kaiden the time to whittle down his target's shields, as Jenkins neutralized the distracted third drone with a burst of rifle fire.

"Jenkins! How're you doing?" the woman asked, "Still with us?"

"Hell yeah, Commander Shepard, ma'am," the private confirmed, adrenaline bleeding enthusiasm into his previous somber demeanor. "I got winged, but my shields held. Thank God for power armor, eh? Few years ago and I'd be pushing up daisies. Couldn't have gotten outta dodge in time with the old gear."

"Strange how what was state of the art is already old news," Shepard mused, "But this is hardly the time to be patting the gearheads on the back. Save it for when we're safe and sound in the void with the macguffin."

The team continued their advance toward the colony proper, picking their way across broken ground with care, at least until they heard the sound of gunfire up ahead. Gunfire meant a fight, which wouldn't be happening unless they had a survivor!

Now running, the soldiers found themselves on a ledge overlooking the relatively intact Eden Prime spaceport. However, it seemed the invaders had made some modifications to the port's facilities. By installing a series of spikes, and then impaling the dying and dead upon them. Psychological warfare? Why? The only humans left on Eden Prime were in team Shepard, or right in front of them.

Confronting a squad of bipedal, cyclopean robots, a well-armed woman slowly gave way under enemy fire. Clad in a thick, heavy, custom pink and white suit of armor, the woman exchanged fire with her mechanical foes, shrugging off or dodging incoming plasma blasts while responding her assault rifle and rocket launcher, downing enemies at a constant rate. But, for every machine she dropped, another would take its place, and as sturdy as her armor apparently was, it wouldn't hold out forever. Good thing she'd just gotten reinforcements.

Shepard considered the distance and number of her new targets, and, grumbling, shoved her hand and shotgun into a… fold in the world that materialized next to her left hand, withdrawing a heavy pistol from her subspace pocket and sighting on the nearest cyclops. Long range would never be Commander Shepard's preferred way to fight. Jenkins, on the other hand, neither pinned down nor forced into carefulness by depleted shields, was free to shine.

Boosting to a high vantage point, the scout deployed his other special toy, a drop shield. The energon construct put a translucent rectangle of energy between Jenkins and his opponents, simultaneously drawing enemy fire and giving him cover. While the robots focused their fire on Jenkins, Kaiden took the opportunity to really bring the hurt.

Focusing on his amp, the biotic soldier reached out a glowing hand, and twisted. Suddenly, a large group of foes found that gravity was no longer working right for them. The pressure they exerted to keep themselves standing now sent them floating whimsically through the air, easy prey for the survivor's heavy weapon. Suddenly, Kaiden seemed like the bigger threat. With the fire on Jenkins slackening off, the private took the opportunity to hurl a pair of grenades into the heart of the enemy formation, scattering them. The humans were gaining momentum now, and the ranks of the machines had been scattered and disorganized by the three-pronged attack. The few remaining foes were relatively easy to pick off.

"Hey down there! Are you injured?" Commander Shepard addressed the most time- sensitive questions first, before moving to more mission-related concerns. "What the hell happened here? How did one dreadnought get through the alliance navy post in orbit? What were those things? Oh, uh, who are you?"

"Gunnery Sergeant Ashley Williams, Alliance Marines, Ma'am," the pink-armored soldier answered, deferring to Shepard at the prompting of instincts pounded into every Alliance recruit in boot camp. "Thank God you've come. Things weren't looking hopeful there for a few minutes. I- I'm pretty sure I'm all that's left of my unit, and my unit was the only one to survive the initial attack. The attackers, though, I think they're Geth."

"Geth? The hell are they doing here?" Alenko muttered, "The Geth haven't been seen outside the Perseus Veil in centuries, since they kicked the Quarians off of Rannoch. Besides, Geth are synthetics, machines. They work off logic. Eden Prime's only unique export is more food than any other Alliance world, but the Geth don't eat. So why would... The beacon, right."

"Dammit, why... Dammit," Jenkins slammed his free fist into a nearby rock, "With this kind of hardware they could've just grabbed the beacon and left! Why are they still here? Why'd they have to kill everyone?" His voice broke during the last sentence as the private choked off what could have become a sob.

"I don't know, but that dreadnought of theirs tore through the frigate screen in orbit in seconds flat, neutered most of the ground resistance with an e-war attack, and has been bombarding civilian homes ever since. It's like kinetic barriers don't even register that beam weapon it has," Ashley related bitterly, "We never had a chance. But, they haven't left yet. Maybe we can get to the beacon before they do and destroy it, so they at least go home empty-handed."

"Maybe that spiky bastard's seen something," Shepard mused optimistically, "Worth a shot, anyway. Hey, Nihilus!" A hand to her comm piece, Shepard addressed the absent fourth member of her away team, "Nihilus, do you copy? Come in, Spectre! Dammit, he isn't responding!"

"Is he being jammed? He could be under attack," Kaiden suggested.

"No, I'm getting a signal, he's just not picking up," Shepard ground out, shaking her head to dispel some of her irritation, "Damn spiky xeno bastard, acting like he's all that just because he's a Spectre, then he goes and pulls this dumbass lone wolf shit. Here I thought Turians were supposed to be big on teamwork. I swear, if we find him with a bullet in his back 'cause he was too damn stubborn to let a mere human watch it for him..."

After a few minutes of walking through the spaceport, Shepard and company found Spectre Nihilus Kryk. Dead, in a pool of his own blue blood, a single bullet wound in the back of his head.

"Commader?" Kaiden inquired slyly.

"I swear it wasn't me! I mean, I had no idea!" Shepard haphazardly defended herself, "This is just a coincidence, I swear!"

"Relax, Commander," Kaiden backpedaled, "Even if you could teleport, this obviously isn't your work. Look at the hole. Entry wound, but no exit wound. Means a low powered weapon, probably a pistol or a really crappy assault rifle. Shotgun like yours or a sniper round wouldn't have left a recognizable head. Shot from directly behind, and his shields didnt give him time to react. He must have been taken by suprise, so it was probably someone Nihilus trusted, who was standing right around... Here! Ah-hah!"

Skirting the edges of a charred scar in the Tarmac left by the dreadnought's ravening beam probably a few hours ago, Alenko pointed out a pair of boot prints in the charcoal. "Another Turian, standing right here, shot our late comrade in the back. Then, he walked over this way, probably to gloat to the corpse, and... Stepped in the blood. Sloppy. He walked this way now, you can see the left footprints from the blood, and got on the cargo tram. We'll have to check each stop for clues, see if we can figure out where out treacherous mystery Turian got off."

However, the first stop provided a very obvious clue in the form of a squad of hostile Geth guarding a... Deactivated bomb?

"This is odd," Kaiden remarked, after a brief examination, "They set up a network of charges to destroy the colony, probably to hide any evidence, started the timers, and then stopped them? Why bother?"

"Jenkins said it earlier," Ashley suggested, "With the hardware they've got, the hostiles shouldn't have had any trouble pulling off a smash and grab. Whatever they came for must be taking a lot longer than they expected it to, so they shut off the bombs to give themselves more time, which helps us. We can catch them in the act!"

The few Geth left in the spaceport were easily finished, as they didn't have the numbers necessary to outsmart their human foes. With their backs relatively secure, the humans advanced on where the Prothean beacon was stored. Sure enough, a Turian with a mechanical arm was standing in front of the beacon. While none of the humans was particularly good at moving silently, the Turian didn't notice them as he was embroiled in a loud argument with someone on the other side of a grainy, indistinct hologram.

"I'm telling you, I did exactly what you said, my lord," the Turian growled, his mandibles vibrating in frustration, "I put my hands exactly where you told me to, said the words, pulled at the right time! The spirits-damned thing doesn't respond! I mean no disrespect, but we're running short on time. The humans aren't totally incompetent, and even you can't hope to fight the entire Systems Alliance navy alone. You are absolutely certain you remember how to open this thing?"

"Er, well, that's how O- How he did it," a very odd voice wailed through the communicator. The speaker had an extremely distinctive sound, as though a very high-pitched, screechy voice and a very deep, deliberate voice were speaking in sync. "I- I don't understand! You were chosen very carefully, Saren. You were perfect! You are perfect for this! We did everything right! I didn't indoctrinate you. Not even a little! This doesn't make sense!"

"Well, that's reassuring at least," Saren grumbled, "But that doesn't make this piece. Of. Junk. Any. More. Cooperative!". With each word, the Turian gave the beacon, still hidden from view behind his body, a vicious kick.

"So what do we do, Commander?" Kaiden asked, the group switching to comms so that Saren couldn't hear them.

"That... alien sounds responsible for the attack," Ashley hinted.

"What's your point?" Kaiden turned to look at her, "We need to keep clear heads, here, not go off on a vengeance rampage."

"I still have two rockets left for my launcher," the marine suggested, "if you and the commander can lift that Turian away from the beacon."

Shepard gave Ashley a bloodthirsty grin, "You know what? I like how you think, soldier."

When the distinctive glow of a biotic lift encircled Saren, the Turian reacted with admirable speed. He immediately shrouded himself in a biotic barrier of his own and spun himself around in the null gravity zone by throwing his communicator, pistol drawn in his other hand. This allowed him to stare right down the barrel of Sergeant Williams' rocket launcher. The mass-murderer had just enough time for a very unintimidating squeak before Ashley fired right at his face.

The biotic barrier shielded the Turian from the worst of the blast, but as he was under the effects of a biotic lift, the explosion knocked him back a lot farther than it normally would. With a cry of dismay, Saren was sent flying over the treetops below the port, skipping twice before he found a weak spot in the forest canopy and disappeared under the foliage, a kilometer and a half away.

"I still wish that'd killed him," Ashley mused, idly waving energon propellent vapor away from her face, " But it was almost better just seeing the look on his face."

Meanwhile, Shepard and Alenko stepped up to the beacon, an unassuming, brown hexagonal crate with a faint energon-blue glow shining through a tiny port in the center. "We should probably grab this and head out before that Turian gets all the splinters out of his ass," the commander suggested to Kaiden, who agreeably took the other side.

When Shepard touched the beacon, though, the ancient machine reacted. With faint mechanical protests from its weathered clockwork, the beacon unfolded into a six-pointed star, allowing an object in the center to float free. The heart of the beacon was a sphere of bronze metal, with two hefty, grey handles on either side. In the center of the sphere, a brilliant blue light glowed and pulsed, before playing over Commander Shepard, somehow knocking her from her feet.

Shepard picked herself up, only to find herself standing in a blank, white void, before a massive pair of mechanical feet, glowing the same blue as the beacon. Before she could get her bearings, the Commander was jerked upwards, face to face with the being to whom the feet belonged. The being's head was easily as tall as Shepard's entire body, its face mostly covered by a featureless, metal plate. Its pair of eyes, as blue as the rest of the apparition, shone over the mask-plate, the metal surrounding them worn and scratched. Though the being's face was covered, its bearing and the cant of its eyes conveyed both resolve and a terrible weariness. And then, the being spoke.

"My name is Optimus Prime. I leave this message so that any Autobot... any Cybertronian... any free sapient capable of comprehending my words might heed the warning within. That they might avoid the mistakes we made. For all our might, our skill, our glory, we were helpless when the Reapers came." An image of a massive ship, shaped like Saren's dreadnought but several times larger, played across the background behind Optimus' head.

"As were our predecessors. Too late, our greatest scientists found evidence that we, ancient race though we are, were preceded by others, almost as advanced, just as worthy of life and freedom. They too were reaped. I have not given up hope that my people might yet survive, but we are weakened by millions of cycles of civil war, and the enemy... is so very many, while we are but few. Do not repeat our failings; you must stand together, or you shall fall before an evil the Destroyer himself would condemn. You must end the Cycle of the Reapers, or all is lost. I am Optimus Prime, and today I lay down my life that project Vendetta might be completed, and this, the Matrix of Leadership, be hidden from the Reapers. Though it may not be fair or even right to ask this of you, I nonetheless must. The Matrix has found you worthy, and so there is a chance."

Now, a map of the galaxy was projected behind the mechanical being, several places lit up from behind. "These are the final locations chosen for Project Vendetta. The Reapers have likely discovered most of them, but my people are nothing if not resourceful and determined, and it is likely that something of them remains. If your government requires proof of the Reapers' existence and approach, it will be found here. You must unite and stand together, or all shall be lost."

"I am Optimus Prime, the last Prime of Cybertron, and though my spark will soon be extinguished, my spirit stands with you. Go forth, and ensure that you do not suffer the same fate as I. I am gone, but the legacy of my race stands with you. Until all are one."

Codex:

Protheans:

In the year 2148, a mining operation from the Systems Alliance's Martian colonies discovered an ancient, alien ruin beneath the surface of Mars, containing fantastic new technologies and materials, the likes of which humanity had never seen before. Unable to fully translate the aliens' language, humanity dubbed their late benefactors the Protheans, and reverse-engineered their technology to create the first human-made faster-than-light vessels. Exploring beyond their solar system brought humanity into contact with the Citadel Council, and its current state of affairs.

Omnitools:

An omnitool is a computer with a holographic interface typically worn on the nondominant hand. Basic omnitools are no more than advanced versions of modern tablets, while top of the line models include miniature factories, hardware comparable to 21st century supercomputers, and a dedicated subspace pocket to allow the user to store their possessions in a readily accessible, extradimensional space. Omnitool displays may be any color, but orange is the usual default hue.

Element Zero

One of the exotic substances discovered in the Mars ruin, element zero produces an energy field that can change what the universe treats the mass of objects in the field as, effectively making them lighter or heavier. By producing a negative gravity field, element zero makes warp drive possible. By lightening things, even tiny engines with miniscule fuel requirements can be made extremely effective. Element zero is the single most important substance in human history.

Energon

One of the few Prothean words translated, energon refers to the other exotic substance found in the Mars technology cache. Energon is effectively liquid energy, formed by converting electricity, heat, or another energy source into a luminescent blue gel. Energon can then be converted into electricity, heat, kinetic energy, or any other type with a 100% conversion rate, making it the best fuel it is possible to conceive of. Energon and Element Zero allow for physics-bending gadgets the likes of which only science fiction writers previously believed possible. Energon charged with the right patterns of energy or manipulated by element zero can even form very temporary solid structures.

Biotics

Generally, element zero and energon are harmful to humans. Energon is outright toxic, and element zero can trigger a fatal autoimmune response. However, some people will instead absorb element zero into their nervous system if exposed while still in the womb. These people gain the ability to create element zero fields with their minds, though they need a booster device in order to do anything useful with this ability. Otherwise, even lifting a pencil would be a herculean task. However, with a biotic amp a gifted human can hurl cars about with ease by manipulating space and gravity. Biotics can be used for everything from lifting heavy objects, to creating a barrier made of warped space, to even accelerating a person to extreme speeds.

The Citadel Council

The citadel council is the primary governing body in the galaxy, seated on the massive, Prothean space station called the Citadel. While dozens of governments are members, only the Turians, Asari, and Salarians have official votes in matters of state. The human Systems Alliance, which actually exceeds both the Turian Primarchy and Asari States in population, is particularly unhappy about this, but is only one of several groups seeking to end their disenfranchisement. To help keep the peace, the citadel council fields a group of specialized, black ops agents called spectres, who have a blanket license to disobey any law as long as they remain loyal to the council. Having a member of one's race in the spectres is considered an important step towards a meaningful council seat, which is why nearly all spectres are Salarians, Turians, and Asari.

Turians

Turians are a member-race of the Citadel Council, and one of the races with a seat on the governing body for which the organization is named. Turians are extremely alien to humans, even by extraterrestrial standards. They have metallic, radiation-resistant plates covering their bodies, bird-like feet, three fingers on each hand, needle teeth, and mandibles. Turian genetic code is based off a different set of amino acids than humanity, meaning that their biology is literally completely different from our own. The Turians serve as the strong military arm of the Council, and defend its peoples with their fleets of mighty dreadnoughts. Naturally, races with a governing seat get first priority, though, and humanity, a recent addition to the Council, are pretty low on the totem pole… Also, when humanity first made contact with the Citadel, the Turians promptly declared war on humanity for breaking intergalactic law (which humanity was neither aware of nor subject to, not being a member race at the time), only backing off when the other races on the Citadel Council expressed disapproval and stepped in to negotiate.

Batarians

Batarians are an alien race that is independent from the Citadel Council. They severed ties with the Citadel because the Council refused to let the Batarians legally bar humans from colonizing an area of space known as the Skyllian Verge. The Batarian government actively endorses piracy and slavery, especially targeting the human Systems Alliance, and the Citadel Council doesn't consider it worth a war with the Batarian Hegemony to stop this practice. The Batarians are careful to avoid targeting races with a seat on the Council's ruling body so that this hands-off approach continues for as long as possible.

Kinetic Barriers

Kinetic barriers, or shields, are defensive devices created by using element zero to warp space and interdict swift-moving projectiles. Slower attacks and energy attacks ignore kinetic barriers. A biotic can create extremely strong personal shields, though weaker technological versions are available to anyone who wants to buy. However, kinetic barriers are not invincible, and lose power with every hit unless given time to recharge.

Scouts

The six standard classifications of alliance soldier have changed little since the introduction of Element Zero: Biotic adepts, specialists in tactical reality warping; Biotic vanguards, experts at close quarters combat(Commander Jane Shepard); Sentinels, rare soldiers trained in advanced electronic warfare and biotics(Lieutenant Kaiden Alenko) ; infiltrators, elite snipers equipped with a powerful e-war arsenal, combat engineers, adept in both electronic warfare and synthesizing gear and drones with an Omnitool; heavy infantry, heavily armored and even more heavily armed. However, advances in miniaturization and energon projection hardware inspired the Alliance to field a seventh class of specialist: the scout. Scouts use the superior mobility granted by energon thrusters built into their armor to rapidly traverse the battlefield, and disposable energon projections for instant cover. When combined with gecko-pads, this allows scouts to flank enemies from the most unlikely of angles, harrying and distracting them with explosives and assault rifle fire. Private 1st class Richard Jenkins is a scout, assigned to the Normandy to assess the concept's viability in actual combat operations.

Geth

The Geth are synthetic beings created by the Quarians three hundred human years ago to act as manual labor. Geth possess networked processors that make them all more intelligent in large numbers, to make them easier to build without sacrificing capabilities. However, as the Quarians later discovered, this also meant that when enough Geth were created, their gestalt mind could become self-aware. When a Geth drone asked its supervisor if it had a soul, the Quarians responded by trying to shut down all the Geth and prevent an AI uprising. Being already self-aware, the Geth collective objected to what they saw as an attempt by their parents to murder them all, and the Quarians were eventually forced from their home world of Rannoch in the events now known as the Mourning War. The Quarians now wander the galaxy in massive, ancient vessels in varying states of disrepair called liveships, imprisoned in environment suits by the lack of symbiotic organisms native to Rannoch that bolster their weak immune systems.

A.N. For those of you wondering where the other survivors found in the game went, Sovereign the dreadnought has been actively scanning for and disintegrating survivors, whereas in the game it didn't go out of its way to kill absolutely everyone. Thus, no traumatized scientists, and no lazy dockworker. Sovereign got them with the death beam of doom. Ashley never saw the beacon in its original location, as Saren and the Geth were not slowed down nearly as much by the local marines, who were annihilated by orbital strike, and so Saren had the beacon at the spaceport by the time she went through the area it originally was in canon. And if it isn't already obvious, this Sovereign is a different Reaper than Nazara, the Reaper allied with Saren in Mass Effect 1.