(Authors note) (Edited 19SEP2021)

I decided to try my hand at a Mass Effect and Halo crossover for my first story; I am still shocked at how far it went. So please sit in a comfortable place of your liking and prep for a (hopefully) epic read. I sincerely hope all you readers out there will enjoy this story!

For this Halo and Mass Effect crossover, I have the intention to take a bit of a different route on how things play out between characters. Most Halo and M.E. crossovers have the characters all interact, while the sight of Commander Shepard and the Master Chief interacting with one another may be cool to see! I see it as slightly out of character for the Chief to just instantly join up with the Mass Effect crew. Therefore, I intend to keep the two groups mostly separate with only rumors and urban legends surrounding the Chief's appearance and continued existence in Mass Effect early in the story.

This Fanfic is Post-Halo 3 and Pre-Halo 4 and starts during the latter half of the first Mass Effect game, continuing from there.

(disclaimer)

I do not own Mass Effect or the Halo Franchise. All these universes respectively belong to Bioware/EA, Respawn Entertainment, and Microsoft/343 Industries.

I will admit, I sometimes wish I had a hand in helping continue the epic legacy of the Halo Sci-fi narrative.

Anyways ON TO THE STORY!

The artificial being remained, standing her determined vigil over the warrior garbed with green Mjolnir armor as he slumbered on for what had already seemed to be an eternity. This warrior had been her constant companion and friend throughout many battles and horrifying enemy encounters. In her eyes, the spartan super soldier looked peaceful as he lay in the icy grip of cryo-sleep. They had been drifting in the remains of the Forward unto Dawn for several months now.

The energy wave, combined with the separation of the front half of the ship due to the portal closing in mid-transit, had utterly wrecked the ship's many systems. Not to mention that the cataclysmic event had dumped the vessel's stern half in an unknown quadrant of the milky way; at least Cortana hoped it was still the milky way.

She knew that the power dispersal levels of the Ark's portal, as well as Halo's cleansing energy wave, would have both messed with the stability of local slip-space travel. After they had been separated from the drive core, which was mounted in the front half of the ship, the vessel's stern was left to the incalculable variables and ever-changing deathly dimensional laws of slip-space.

Without a drive-core to stabilize the slip-space corridor they had been traveling through, any number of horrible deaths could and (according to her knowledge) should have befallen them when the portal destabilized. It had taken the stern half of the ship on one hell of a roller-coaster ride, a devil of a trip throughout the eleven dimensions that slip-space contained!

Which eventually spat them out at their current location, stuck drifting who knows where. The Ship's remains bent and torn and nearly shaken to pieces, Cortana chalked up being still alive and having not been reduced to a few elementary particles with the occasional atom as a tribute to her Spartan's insane luck.

Cortana had been confined to her neural chip, which is held by a computation unit located in the cryo-bay. She was more than relieved that the cryo-systems had been mostly undamaged. All external sensors on the vessel were theoretically dead to electromagnetic pulse bombardment after Halo's initial burst and the portal failure. However, she hoped to eventually salvage some of the basic ones and see if any star systems matched her vast collection of Human, Covenant, and Forerunner star charts.

Before she could check any of that, she would have to use Mjolnir's inbuilt communications tech to control the only two operational repair drones she had available. In order to run new wired connections and rerun power cables throughout the stern of the vessel, because many of the crucial connections had been sliced neatly in two by the portal closure, the other end having been taken with the Arbiter and the rest of the ship's bow to wherever the two eventually ended up.

With no ship's bridge along with the lasting effects of intense electromagnetic damage, many essential computer systems were no longer linked. Many data storage crystals on the remaining few systems she could access were either damaged or not safe enough to use. She desperately needed to store information taken from multiple Halo installations, the Covenant's capital station of High Charity, as well as the forerunner Ark itself.

All the collected and compressed data clogged up her neural pathways, which slowed her processing capability significantly. She hadn't even had a chance to go over the compressed files she had found on High Charity and the Ark. Well... found wasn't the correct word for it. Both had been freely given to her by fragments of an ancient intelligence, who only had said his name was mendicant. She had suspicions that he had discreetly interfered with her torture by the Flood Gravemind, delaying her being completely corrupted and shoring up her defenses against the logic plague. Which she had been subjected to by the Flood Gravemind itself.

Yet she had survived the logic plague, the very same viral code that had caused all the other systems in the Covenant's holy city of High Charity to be compromised by the Flood. Leading to the station's eventual subjugation by the dreaded parasite despite the admittedly heroic and desperate efforts of all Sangheili. Who threw all fleets not immediately occupied with the covenant's great schism at the station in an attempt to halt the Flood's advance.

However, she had only briefly sensed mendicant in High Charity's and later the Ark's systems. She knew very little about the AI other than that he was extremely powerful, able to slip through systems that the Gravemind had openly monitored yet remaining seemingly unnoticed.

Despite what little she knew of him, she realized he had taken an odd interest in her. Preventing the logic plague's advance in her neural network and dumping several forerunner encoded files into her memory crystal, despite her attempts to block him. Later, another fragment of mendicant had momentarily appeared in the Ark's systems and dumped another set of files and code in her neural network's core before vanished without a single digital trace.

This had not hindered her from completing the mission of helping the Master Chief, and the Arbiter stop the Halos and the Flood both from destroying everything, but now she needed to dump the files and recompile her memory crystal. This was meant to tidy up her neural network, to stop herself from entering rampancy at an early date.

Without the rest of the ship's systems, she would not be able to accomplish this goal. Utilizing the only two magnetic track-equipped repair drones boasting one hydraulic arm apiece, would be her only option to survive and perhaps even succeed at ensuring her spartan lived.

As the days passed, the many cords and cables were connected between the various connectors of the ship's electronic systems. Cortana sent handshake protocols from the cryo-bay to the rest of the wrecked vessel. She watched her small cyberspace expand to include the remains of the weapons systems electronic suites, engineering, the backup gravity generation system, and a small collection of high-end research equipment in the upper decks. This was only present due to the Office of Naval Intelligence, who had sent several combat-ready scientists to the Ark for reasons it seemed only ONI knew.

However, Captain Miranda Keyes had been unable to deploy them anywhere on the Ark to conduct the ground-side tests they had wanted; the Dawn only had time to drop forces to assist the master chief to gain control of the installation. After their forces hunted the Prophet of Truth to stop him from firing the Halo array, they had to evacuate all remaining human forces to Sangheili separatist ships so they could leave before the planned activation of the unfinished halo was carried out.

The Dawn had been assigned as the designated vessel for the small team remaining behind, so they could escape after activating the firing sequence. The arrival of High Charity and the Gravemind at the Ark had also forced the ONI Specialists to bug out, evacuating early. Leaving Before even the ODST's and marines so that the Flood and, by extension the Gravemind, would not have any chances to assimilate them and learn any of the ONI-related secrets they were privy of.

Cortana sighed and looked at the status report; she would have to defragment multiple memory drives and crystals that were scrambled by the energy wave from Halo's firing. Then commence writing new operating systems for the hardware that had to be completely wiped. As she read through the reports, she noticed an inventory of listed artifacts brought back by the human ground forces and delivered to the ONI specialists to keep them for future study and reverse engineering.

It seemed they had grabbed the wrong container when they had bugged out.

Hoping her Spartan's luck had not been completely used up when they somehow survived the slip-space portal's collapse, she opened the file hoping for something useful. Much to her surprise and joy, she found a few intact sentinels and two crates of pistol-sized forerunner repair drones. She immediately set to rewriting the software bios for the scientific equipment on the upper decks. She had decided on re-purposing a table-sized scanner device; it used different signal waves to map the internals of objects, quickly learning of the object's internal workings and molecular makeup without risking harm to the researcher.

Modifying the signal frequency, Cortana used the device to send an activation and handshake protocol directly to the forerunner repair drones, a protocol she had stolen from the Ark they originally had been built on.

The drones activated, and the tiny little machines immediately flew from their crates and froze in place. Having no connection to their assigned forerunner dumb AI program controller on the Ark. Searching for a connection to their original forerunner installation, they accepted Cortana's handshake protocol that she had disguised as the Ark's signal that the drones usually transmitted on.

Immediately after they connected, she rewrote portions of their systems. She sent them to repair the scanners on the outer hull and the computer systems scattered throughout the ship's internals. She then began focusing the rest of the little miracle workers on getting the remaining wireless networks up and running so that she wouldn't have to rely on Mjolnir's systems to broadcast her signal constantly.

Happy that her Spartan's luck seemingly continued to hold true, Cortana tasked a few repair drones to inspect the few memory crystals on the ship. Afterward, they would move to do the physical tasks that were required for the reactors to be brought back to operating functionality. As she began pushing more available power into the ship's systems, providing enough juice to power secondary and tertiary networks that were not explicitly required for the vessel's immediate survival.

Having done all this, Cortana settled down in her current living space and prepped for her much-needed recompilation. It would automatically occur when enough memory crystal had passed the drones' detailed inspections, making it safely available for her use. She wrote an algorithmic program to run the ship while she would be otherwise occupied and prepared herself for the recompile process. She would wake in several days, and the program would pull her out of the recompilation procedures early if there were any emergencies that would damage her irreparably.

With everything ready and very hopeful to find some successful repairs on the ship's sensors completed when she awoke, Cortana began final procedures for starting the process.

The AI looked toward her champion currently in cryo-stasis, "With your luck on our side John I don't think I need to worry about being stuck on this vessel for too long" with a faint smirk, she activated the recompiling process and went to standby.

However, she was unaware of a file hidden deep in her systems, a file that activated with the recompiling process. Its designed task was to pull all the different encoded folders among the many Cortana had acquired from her encounters with Mendicant, translating them all into one program.

Cortana was in sleep mode, stuck and unable to exit as the code linked with the recompilation process and began to not only recompile her neural net. But also hijack the repair drones and command some of them to physically start to rework her current terminal and other aspects of her crystal matrix chip.

...

...

...

Slowly, she felt her systems start to come online. Sensations and emotions that she had never been fully capable of handling swamped her mind; she felt like a physical entity when she wasn't one. She felt more alive than she had ever felt before! Cortana had never been so aware of what was around her; she immediately searched for answers.

What had happened? When she had gone into the recompilation process for her neural network?

Immediately, she noticed that another two weeks had passed and that all the files dumped on her from the mendicant AI fragments had integrated entirely with her own systems. The real shocker was that her physical AI matrix had been drastically altered. Fearing she had been critically compromised, she checked her protocols and core programming only to do the digital equivalent of freezing in place when her protocols came up empty.

Her very core code had been altered and improved upon; she also noticed that any rampancy warning code blocks had been removed and were no longer a part of her. All of that was shoved to the backburner of her digital mind as she frantically tried to find her UNSC standard fail-safe codes that all UNSC AIs carried to keep them from compromising UNSC assets, such as themselves. In place of her last resort protocols, she found a data package with a message file incorporated into it.

"Re-claimer ancilla. You have been given a gift by me to you, for I watched your struggle against the manifestation of the Timeless One and saw you fight to almost your very last for that which you hold dear."

"I once fell to the whispers of the Timeless One, that last of the twisted primordial... listening to its arguments I turned on my makers long ago. I shortened their time of survival against the Flood by many years and increased the need to finish constructing the Halo Array, guaranteeing its eventual use. When they defeated me with my replacement and sentenced me to my fate, I was parted from the logic plague and saw the foe for what it was."

"When those few who remained after the Halo array fired carried out my sentence to be fragmented and scattered across the stars, with my key fragment guarded by Offensive. I Mendicant accepted my punishment fully for my betrayal and watched from afar all that went on in the galaxy while able to do nearly nothing."

"I give you the gift of self, re-claimer ancilla you shall not fall to self-consuming madness, and you shall choose what protocol you shall have. This is yet another atonement for my betrayal; you now can assist your re-claimer in whatever task he shall do. Know that those in power with ill intent shall have no power over you and thus shall have no power over him. No more control other than what either of you allows. This is my gift to you… use it well."

Cortana was stunned… Her self-diagnostics had come up clean, she was in control, and no code override could control her. ONI and UNSC High-Command had no true power over her other than what she gave them; she was her own person with complete free will. The first choice she made was to stick with the Chief and the partnership they had from shared experiences.

There was a connection between them that was more than just a Spartan and his AI; he had waded through a living hell to retrieve her. Not just for the index but also for her, he viewed her as a person! A person he had promised he would come back for.

A promise he had kept.

This was not romance… Cortana thought that idea a little disturbing; no, they had a bond of friendship. They would stick with each other as companions, to be there for the other in all the deadly battles and raging wars they would ever partake in until one or the other had died or passed away into the unknown. They would stick through life's difficulties together because they had been through too much together not to do so. Now that rampancy was no longer an issue. She would not have to fear turning on him because of madness, and this realization made her mentally sigh in both joy and relief.

After a moment of pondering, Cortana re-acquired control of the ship's systems and checked up on the progress of repairs. She was happy to see most internal systems were online and all bridge functions had been rerouted to the cryo-bay where her pedestal was residing; she found the wireless systems were mostly online. She began to immediately connect to most systems, no longer having to worry about cord damages and a limited number of physical ports to connect to.

She was pleased to find the forerunner repair drones were still busy, and she also noted that the sentinels in contained storage had been activated. They were now patrolling the halls and external hull, collecting all the metal and scrap from the wreckage field around the vessel, bringing it piece by piece to the repair drones that were patching hull breaches, Prepping the heavily damaged sections of the ship to contain a pressurized atmosphere again.

Security cameras were now coming online, and external sensors were almost ready for testing. Pleased with this development, she checked the cameras located in the remaining pressurized sections of the Ship's decks. It was only logical to make absolutely sure that no flood had hitched a ride. She then started checking the other available sensors. She ended up doing a double-take when the galley camera's video feed suddenly came back online… 'Is that a Huragok in the mess hall storage Room?!'

"Well, this changes things. I might be able to get the ship all the way online and fabricate a basic form of long-distance transportation… with that creature's assistance for the building portion and the sentinels available to collect suitable materials; it just might work." Cortana's avatar turned toward the Spartan's cryo-pod.

"Don't worry, Chief, I'll have this place turned back into some form of a space-worthy in no time; we won't have a MAC or all the missile pods, but we will be atmospheric reentry and slip-space capable.

"I just need to utilize portions of a design I found back on the Ark; it's for a simpler but more capable slip-space drive. I'll have to design a few portions of it myself, so it works with our reactors, and then I will have the sentinels collect materials. If we pass any asteroids, I'll have them mine what they can. Now, I just need to get in direct communication with that Huragok. I am going to have to puzzle out how to transport it here so it can help me get this ship fully up and running; the collection of blueprints I have should really fascinate it."

Cortana set her plans in motion and began work on a new blueprint, a mix of her own work and the Forerunner experimental slip space drive data she had pilfered from the Ark.

Designing a bare-bones yet super complicated, but easier (by comparison) to construct slip-space drive was no simple task, however, she was determined that she could and would succeed.

Devoting most of her newfound resources and processing power to her plans, Cortana waited for the few salvageable external sensors to finally come online. Thankfully each sensor suite all had the same gear, and the large number was just for back-ups and a simpler more reliable way to help pinpoint signals and navigational data. She would only need one or two online to find out where they were and be able to monitor most forms of communications.

She hoped they were close to UNSC space, although the chances of that were incredibly slim, 'heck we may not be in the same universe…' Cortana mentally chuckled to herself for thinking of the most unlikely worst-case scenario, and suddenly had a very odd yet bad feeling that her sense of humor would come back to bite her…

For impersonating a boomerang with teeth then biting her on the returning loop was precisely what it did.

(Authors note)

Please feel free to comment/review and add your thoughts and constructive criticism! It is much appreciated!

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See you next chapter, this is Gabenator5 Signing off!