Harvester (Skyline)

The Aliens are a hyper-advanced extraterrestrial species. These aliens are most commonly seen as black cephalopod-like creatures with the ability to transfix and utilize the brains of different species to power themselves. However, since it's shown that the Hive Mind itself is bipedal and somewhat humanoid-like, it's possible that the cephalopod-like aliens are merely either the aliens' servants or creations. They are responsible for the creation of Humankind, which acts like crops for them to harvest brains to build their army for millions of years.

History
The aliens created the human race long ago as a means to harvest human brains in order to build warriors. After millions of years have passed, they arrived on Earth and began their global harvest, using their brains to power themselves up and building their army by placing human brains into various bio-mechanical structures. They managed to "harvest" most of the human population and the surviving humans formed their newborn resistance out of both the desire to fight back and fury for the loss of their loved ones and friends.

After the good red-light alien Trent used a Tanker to kill the Hive Mind in charge of the Earth-harvesting force, a decade later the humans, led by the evolved Captain Rose, manage to master the alien technology and organize the resistance against them in space.

Drones
The Drones are squid/octopus-like aliens with slimy black skin, multiple eyes, and glowing lights on their tentacles that they use to bring other species into a trance-like state. Drones have the ability to steal the brain and spinal cords of their prey, and are capable of surviving without a brain but only for a few minutes; during that time either a Drone's tentacle or all of the Drone will approach the nearest target who has a suitable brain. Drones can be destroyed with either high caliber rifles or heavy weapons such as rocket launchers or explosives due to their hard exoskeleton, which makes them immune to small arms fire. Furthermore, pulling the brain of their nerve system forcefully will also kill them instantly, as the injured but strengthened Jarrod demonstrated when he performed this whilst defending Elanie from the Drone he was fighting. The main task of the drone is to harvest brains so the Hive Mind can build Warrior Variants.

Like Tankers, their skin is quite flammable, so a flamethrower can also kill them.

Hydras
The Hydras are black flying aliens that function as dropships. They can either release Drones to find prey or hunt down humans themselves. They have wings, several tentacles trailing behind them similar to the drone, and one big blue eye. What comes as a genuine surprise is that they do not have any projectile-based weaponry, considering how advanced they are supposed to be, and instead utilize a "suicide bomber" approach when combating enemy aircraft. The lack of weapons may imply these craft are not normally used in combat situations and only take on this role when absolutely necessary.

Tankers


These aliens are massive four-legged creatures that function as "mechs". They require large ordinance like rocket launchers or tank shells to destroy them, but their skin is flammable and thus a flamethrower is capable of slowing them down. They're mostly 'gathering' the alive prey much as possible before taking them into a mothership for the use of their brains. It's logical to say they're the main 'gathering' forces of the Skyline Alien Species. The aliens piloting the Tankers see their surroundings while inside using some form of holographic HUD.

Advanced Tanker
This is a version of the Tanker biomech controlled by the Shepherd. It is a far stronger and more upgraded version, not to mention it can fire energy blasts to shoot down large vehicles, such as helicopters, as well as having a retractable claw and their very own hypnotizing mechanism.

Warrior
The Warrior Variant is the result of an abducted human brain being placed into a bio-mechanical alien body and mind-controlled by the Hive Mind from the mothership. They serve as foot soldiers to the alien race. Due to fact that they are based on human anatomy, their weakness is their necks in which a shot or a stab to the neck will be fatal to them.

They gain enhanced strength from their new bodies as they are capable of ripping humans limb from limb. The Warrior can be free from mind-control of the Hive Mind by an Evolved or if the brain of a person manages to escape the initial hypnosis.

Shepherd
a Shepherd is the commander of the alien forces, who controls and coordinates all the activities of the aliens on a planet ranging from harvesting to attacking settlements. The Shepherd is the alien in their pure form.

Without them, all other alien lifeforms minus the red-light aliens will collapse.

"Evolved"
The light the aliens use for hypnosis can be used to transform humans, giving them an accelerated growth rate and their blood the ability to disconnect the Hive Mind's connection to the Warrior if utilized in a serum-like state. So far, Rose, Elaine and Jarrod's daughter, is the only known Evolved.

Red-light aliens/Hybrids
Red-light aliens are the population of Warriors with human brains who not only remember their human past before becoming aliens, but have both the same humans' independence from the Shepherd and the free will to fight back against the Hive Mind. This type of alien can only be produced if either the human already has built-up immunity to the hypnosis, or the human has been freed by the blood of an Evolved. In contrast to the blue-light aliens of the extraterrestrial species, the red-light aliens can be easily identified when their eyes glow red.

Humans who escape the initial hypnosis will have the high chance to turn into red-light aliens when their brains are put into the Warrior bodies, as was the case with Jarrod after being exposed to and escaping from the alien light multiple times.

Overlord
The Overlord is the supreme ruler of the Harvesters, who leads their entire invasion force across the universe through Cobalt-One. All of the Shepherds answer to her, and command the invasions through her orders.

The Overlord can sprout tentacles from her body during the combat against his opponents, and her super strength which is also strong enough to tear apart human flesh. She used them to kill General Radford. The Overlord was killed by Trent as an act of sacrifice to save Rose.

Abilities and anatomy
Most of these aliens have the ability to hypnotize a host and feed/power-up by "brains" unless a host is blind, as shown with the blind elderly man nicknamed "Sarge". They have blackish-purple blood (the purple hints at hemoglobin). The aliens suck prey into their body through holes or mouth-like orifices. Only the Drones have the 'power' to transfix in this way. Due to its sophistication and seemingly impossible effect, it's far more likely that their hypnotizing light is a technology that they have developed rather than it being an evolutionary trait. They are able to regenerate lost tentacles with great speed. The blue light they generate can also enhance the creatures that escape the initial hypnosis. An example was Jarrod (having been saved earlier from the alien's hypnosis) showing increased strength and aggression, with his eyes glowing blue and the skin/veins around his eyes darkening - just the same as what happened when he was first hypnotized. His increased strength was shown first when he lifted and pinned Oliver against the wall as he vowed to protect his family. It was shown again when Jarrod and Elaine were on the roof before been attacked by a drone. When the alien attacked Elaine and tried to take her brain, an injured but strengthened Jarrod knocked the alien off her before physically attacking it by hitting it with a breeze block and then using his fists. Finally, he ripped the drone open before tearing out the human brains it had acquired. Furthermore, it is also shown that creatures escape the initial hypnosis also build up immunity to their hypnotizing light and able to turn into Red Light alien after their brain being put into a Warrior Variant body.

It is shown that prolonged exposure to the alien energy or its hypnotizing light will cause pregnant women to produce transformed humans, like in the case of Rose, who is Jarrod and Elaine's daughter. However, the production of these Evolved will be fatal for a woman due to acceleration of growth within the womb causing fatal childbirth complications. The Evolved are extreme threats to the aliens themselves as they are not only immune to alien mind control, but also can cut the mind control connection between Hive Mind and Warrior. However, the acceleration of growth of an Evolved makes them depend on blood transfusion from humans that connect their DNA with the retractable arm-blade to survive. According to Harper when he researches Rose's blood, the alien DNA is compatible with human DNA, making them able to hypnotize humans with their light, however, the hypnotism and mind control of the aliens are useless against the Evolved.

Technology
The technology of the aliens seen in above New York seems to be a fusion of metals and organic components, suggesting an extremely advanced biomechanically driven species. According to Colin Strause, even the motherships are creatures of some kind with their own DNA. Despite the motherships being considered "living organisms" they do have a fair amount of electronic and mechanical elements such as the fact that when the ship goes down in the second movie it's seen electronically sparking and a metallic creaking noise is heard. The main command center of the ship is nearly fully inorganic with metallic floors and a holographic supercomputer/security system. This suggests they are a highly cybernetic race. Some of the machines/creatures seem to be able to rebuild themselves even after a nuclear strike, though these might be destroyed if the explosion is in the interior. However, it is revealed that the ship can only rebuild itself if the Hive Mind is still around to start the rebuilt sequence using the computer at the control center of the ship, so if the Hive Mind dies, the ship will be permanently destroyed.

This is a list of the more minor machines/variants: The motherships are made with a metal hull and organic substances on the inside, a tractor beam, and the massive blue lights that enable the aliens to hypnotize. They look saucer-like, but with spirals and arches sticking out. They are shown to release Hydras either to find prey or in self-defense, as they demonstrated when they released the aircraft to fight back against the fighter/bomber plane force that the U.S. Air Force had sent.

Their abduction devices are tractor beams that can either suck humans into the Hydras or possibly lower the aliens themselves from their ships. The  'alien sorter' is a thin robot with a blue light on the front and a 3-pronged claw, razor blade, and a tube that sucks up the brains into a room that attaches it to the Warrior Variants. Warriors utilize a retractable arm-blade as their primary weapon, which is strong enough to punch through all kinds of alien bio-mechanical machines. Blue energy bomb-like spheres function as the aliens' "grenades" that can cause hypnotism to humans and a massive explosion that is strong enough to destroy the mothership.

Appearances

 * Skyline (2010)
 * Beyond Skyline (2017)
 * Skylines (2020)