This is a sneak preveiw excerpt from an awesome story I’m writing!
Silence echoed down the long, grey corridor, punctuated only by the soft sound of a pair of power armoured boots pacing warily along the gunmetal coloured floor. occasionally punctuated by the sound of blood or ichor dripping from the walls onto the floor. Mutilated body parts were strewn about as smoke from excessive gunfire hung in the air. There had been heavy fighting here recently, Samus Aran decided as she delicately stepped around a larger rotting husk.
She stopped briefly and used her scanner visor to ascertain the cause of death and what the creature had originally been. ‘Unknown genome type.’ The visor informed her. ‘Previous scans match blood patterns with creature alien databases identified as Sangheili (Elites). Cause of death; multiple wounds from Beta Class Metroid, massive head trauma from weapons identified as UNSC M9OA CAWS Shotgun.’
So the Metroids were active in this area. She’d briefly glimpsed one after her ship had crashed further back in the alien ruins. It had been chasing a terrified human through an courtyard which had been inaccessible from where she had been standing. At the time her arm cannon had been completely out of commission as well; every single beam attatchment had been busted by the crash - she’d had to make do with integrating the primitive concussion based weaponry she’d found in the aftermath of a battle.
Something moved in the darkness ahead of Samus. She carefully moved towards it, sticking close to the wall and selecting the second slot in her arm-cannons selection of weapons. The advanced Chozo systems neatly unfolded the two UNSC MA5C ICWS Assault Rifles - or, to be precise, the firing mechanism, barrels and magazine housings that the intelligent armour had harvested to form a makeshift weapon. She also had a close-range option; three of the primitively powerful shotguns. As the figure in the dark, crouched over and panting softly, grew closer and closer Samus unconciously tightened her grip on the weapon in her left hand; her usually clairvoyant scan visor had only been able to identify this as a ‘Mauler’ -  it was a one-handed version of the bulkier shotguns. Samus felt like she needed the extra weapon, with her jerry-rigged arm cannon severely underpowered and relying on weapons with limited capacity.
The thing ahead of her suddenly stopped what it was doing and looked over in her direction. Samus switched to her combat visor and locked onto the target, pointing her weapons straight at it’s head.
“Please, don’t shoot!” it squealed. Samus hesitated and switched to her scan visor, lowering the mauler. As the armoured human cowered, it’s face hidden by a smudged visored helm, she skim-read the notes her armour conjured. ‘Specimen; UNSC Marine Corps ODST (Orbital Drop Storm Trooper), Rank; Sergeant, First Class. Wounded in the thigh and ankle. Minor sprains in several joints.’
Samus deactivated the visor. “Can you walk?” She asked the Sergeant.
“I…I think so.” he replied, clambering to his feet. He was definitely favouring the uninjured leg. Samus briefly considered carrying him; in her armour, it would be no effort at all.
Something screeched in the darkness close by. Samus snapped her weapons up, her combat visor dropping into place and searching.
“Oh god!” the Sergeant shouted. “They’re here! THEY’RE HERE!”
The screech sounded out again. This time Samus definitely recognized it; a Theta Class Metroid. “Keep your head down!” she yelled as it suddenly swooped out from behind a roof beam, aiming for the Sergeant’s unprotected head. It was foiled by the man’s flailing arms, it’s parasitic claws scratching at him furiously.
Samus knocked it aside as the Sergeant slipped and fell on his injured leg, screaming in pain. She brought the Mauler up and slammed two shots into the Metroid. It must have been older and starving, since it’s jelly like flesh splattered apart and sent the amoeba-like core spinning away to wetly hit the wall.
Samus stalked over to the quivering brain organ and looked into the single remaining sensory limb that plaintively gazed at her. Coldly, she smashed an armoured boot through the Metroid’s core.
A faint whimper brought her attention back to the Sergeant. “It’s ok, I killed it.” she informed him. He didn’t reply, staring down the gloomy hallway. Samus followed his gaze and saw the prowling group of infected creatures coming towards them. Humans, Elites and a couple of the smaller things called ‘Grunts’ - each with a mind-controlling Thetan Metroid enveloping their head and energy-sapping flagella snapping and waving over their shoulders.
The Sergeant crawled back a few paces, fumbling for his sidearm as Samus raised her arm cannon and aimed the assault rifles at the group of monsters. Out of the corner of her eye she saw the Sergeant get his weapon free and pull the topslide back.
He then shoved the barrel in his mouth and pulled the trigger. “No!” Samus shouted as the man’s brains joined the other viscera painting the walls.
The group of Infected turned their attention to her. With a harsh battle cry Samus opened fire with the rifles, sending red hot lead sizzling through the air and cutting apart two of the creatures. The rest charged, sprinting at her with eery Metroid shrieks. She gunned down two more and then the rifles were out of ammo.
She swatted aside a energy-sapping limb with her arm cannon as the first one reached her and rolled aside, sending three body-shattering blasts from the Mauler into the main mass of the thing. It fell apart, twitching as the Metroid tried to control the dismembered corpse.
Another Infected confronted Samus as she whirled to face them; she raised her arm cannon to fend it off as it lunged and blew it’s Metroid brain all over the wall, emptying the last of her bullets as a stray shot ripped the Mauler from her hand. She whirled to face the remaining enemies, dropping into a low combat crouch and preparing to meet her doom…
“Duck.” someone said from behind her. Samus heard the whine of a weapon of some kind powering up and dropped to the ground.
Suddenly the corridor was filled with automatic gunfire from a rotary assault cannon of some kind, bullets whizzing over and around her to tear apart the infected creatures with ease. In seconds it was all over.
Samus got to her feet and swiftly reloaded the assault rifles and retried her mauler as the shadowy stranger tossed aside the massive gatling gun and picked up a stray shotgun. He stepped into the light. “I’m Master Chief.” the shining power-armoured soldier said. “You looked like you could use a hand.”

…And that’s all you’re getting for now! Stay tuned for the rest of this cross-over fan-fiction masterpiece!