I am currently working on a singleplayer series called Usurpation Conquest. It is similar to the famous "Correction Nine theory" custom maps, but this one is about how the Usurpation Forces met humanity in the first place. My series puts an elaborate story on how this happened.
The main character of the series is Dafuur-Isthill-Moorlak, younger brother of Argon-Isthill-Maheen, and next in line for the leadership of the Usurpation Forces and for leading The Great Journey. His race is at war with another equally advanced race called Falkonians. It is because of them that his family was taken away from him and his older brother. They have stuck together since then, but now, they have taken away the last of what held his sanity together. As a young Jektarian, doctors found out that he had a rare genetic "disorder" that gave him the ability to warp time and lift things kinetically, and that anyone near him in combat would temporarily gain this power (though not as strong).
Aloth is the second main Protagonist of the story. His background is unknown, but he has a reputation of modifying weapons and ships for better performance. Although his work is excellent, it takes a long time for him to modify something. He is a great soldier on the field, but he prefers to stay in a nice little building making weapons for the other Usurpation soldiers. He can tell you certain strengths and weaknesses of certain weapons, and which one to use in a situation. He is very helpful in most situations, and will be a great asset in most of the series.
During a reconnaissance mission in Sector 24-B (The only notable planet in that sector is locally known as Earth), carried out on Argon's Capital ship The Annihilator, Falkonian forces ambush the ship. When Dafuur finds Argon's lifeless body, he just loses it. That's the most simplest way of saying it. He just loses it. During an intense fight amongst the ship, the Falkonian forces are winning. After taking out a few enemy forces, Dafuur's suit A.I. system detects a highly-explosive device implanted on the ship. He escapes just before the ship explodes. The force of the explosion sends his drop pod flying far away from the wreckage. After floating in space for a while, Dafuur mourns over the death of what was the last of his family. His suit A.I. system notifies Dafuur of a habited planet nearby. The force of the planet's gravitational pull sucks the pod towards it.
After hurtling through space for a long time, Dafuur lands on a large gas giant known natively as Jupiter. His pod lands in an acidic watery substance that eats away at his pod. He is forced to eject and swim to the surface, through the acidic water. When he gets to land, he takes a moment to ponder where he ended up. He sets off, only to find a small, primitive outpost very close nearby. Dafuur was looking towards a friendly encounter, but fate would have it that the lookout was a little... how should I put it... "gung-ho." As soon as Dafuur gets near, the Sniper takes a shot at him. He is forced to retaliate against the Sniper. After defeating the Sniper, he heads on towards the outpost, where he encounters even more human forces. He takes an elevator down towards what seems like a primitive mining area (yes, almost everything humans have made will seem primitive to aliens, so you might want to get comfy with the word). There is a not-so-primitive android guarding the entrance to the mine itself. After destroying it, Dafuur proceeds into it. He easily demolishes the mining grubs within, and finds a somewhat-hidden door leading to a sort of storage room. There, he finds himself behind a large squad of humans. On the other side is a primitive holding cell with an unknown figure inside. The human Scout at the end notices Dafuur, and then an intense fight commences. After defeating the squad, Dafuur checks the holding cell, only to find an Advanced Usurpation Soldier held within the cell. After freeing the soldier (named Aloth-Semitur-Valad), they proceed down the elevator into a long hallway. They come across a large, primitive hangar filled with primitive fighters. After Aloth & Dafuur deal with the forces inside, they take a ship to head back to the home world.