The "Aliens" are a wide array of subterranean extraterrestial species that are encountered in colonized planets UBW-594244 and UBP1116, and serves as the main antagonist of the Star Warfare series. They are colloquially referred to as "them", the scourge that is threatening the interests of the Human Civilization. Only you, with your high-tech gear, can take them out for good.
The Aliens are hostile when encountered and will attempt to attack the Player. These Aliens are relatively feeble and can be easily exterminated by sustained fire.
Each type of alien drops a different amount of base gold. In general, the more difficult aliens appear to drop higher levels of gold. Base gold drop is also scaled proportionally with the alien's strength, so aliens will drop more gold the longer you survive in Survival Mode. Six out of the eight basic aliens have mutations, or stronger variants, that has increased health, damage, and speed, among other things. Mutated aliens are rarer than their lesser counterparts.
In Co-op mode, the amount of health each alien has increases the more players there are in the match. Here's the formula:
1 Player= 100% of health
2 Players= 150% of health
3 Players= 200% of health
Digger: Fast crawling aliens that aggressively seek you out and use their tusks and teeth to deal damage. They are quite weak and will fall under a few bullets from a weapon that is similar in power to their level. Their true danger is not in quality, but quantity. In Payback, they will move faster and faster the longer they are left alive for. An elite variant that spawns uncommonly has a cyan tint to it and is larger, tougher, and faster. This alien deals melee damage.
Tacorlion: Scorpion-like creatures that hang back at range and use their stingers to launch needles at you. Each needle deals more damage than a single Digger bite. They move slowly and are weaker in terms of health. They can act as a very effective support unit for the alien army. An elite variant that spawns rarely has a cyan tint, is larger, has more health, and has more deadly projectiles. This alien deals bullet damage.
Stalker: Raptor-like aliens that use their strength and dexterity to leap over moderate distances. They are tougher and faster than the standard Digger, but still crumble under sustained fire. While leaping, their standard bite attack deals much more damage. In Alien Invasion, they can leap long distances in straight lines, while in Payback, they can actually change directions while in the air. An elite variant with cyan skin spawns rarely. It is tougher, requiring a concentration of weapon fire, and can leap longer distances. This alien deals melee damage.
Green Lady: Crawling aliens with acid sacs on their backs. They move extremely fast compared to most aliens, and if they touch you and explode they can deal massive damage. Their attack is unique among the aliens, as they destroy themselves in the process of attacking the player. They are easily dispatched and are the weakest of all the aliens in terms of health. A problem players face when fighting Green Ladies is that they can approach the player from behind, in which case they can deal tremendous damage. Green Ladies have no elite variant. This alien deals explosion damage.
Demster: Armored aliens that behave differently between the two games. In Alien Invasion, they will roll towards the player while putting up a shield that halves the damage they take, only putting down the shield while attempting to ram the player as an attack. In Payback, the will waddle slowly towards the player, before initiating a spinning attack that causes knockback and also raises sharply raises its defenses and movement speed. Demsters also can attack by biting, which does not cause knockback. The player is most likely to kill the Dempster after it ends its spin. An elite variant with a cyan body spawns very rarely, having more health and damage. This alien deals melee damage.
Trilobita: A sluggish 'land-rover' type alien that has moderately high health, very slow movement speed and a very damaging attack. Trilobitas (also known as Plasma slugs) will rear their heads backwards and shoot a powerful energy ball that can deal very high amounts of damage if not dodged. This alien also has a very uncommon elite variant that has a pink-purple tint to its shell. This elite version has just 25% less health than Mambulls, and also has increased attack power. This alien does not appear in SW2.
Black Mayfly: Flying aliens that launches what appears to be blasts of fire (needles in Payback) the player. It is the only aerial alien. It launches needles that deal large amounts of damage. It can shoot needles in barrages of both one and three. Black Mayflies are quite weak in terms of health, and they crumble under a few bullets from weapons similar in power to their level. Elite Black Mayflies shoot more powerful needles and have more health. The elite variant is rare. At random times, this alien can shoot three needles at a player. This alien deals bullet damage.
Myth371: Alien with an energy shield that teleports and launches energy spheres at players. It is a support unit that is moderately difficult to kill and has a somewhat dangerous attack. They shoot their projectiles in an arc. When a Myth371 has remained in one spot for an amount of time, it will teleport to a spot near the player and fire again. A Myth371 has medium health, medium damage, and moves very slowly. Myth371s have an elite variant, which has an orange tint around the base of the head. They get more damage and health. This alien deals energy damage.
Mambull: Large, dangerous alien with a resilient hide capable of absorbing extensive amounts of damage. Mambulls charge into the player, causing high damage and knockback. Circle-strafing to maintain constant distance is an effective close-range strategy, but melee weapons are not recommended due to the range of a Mambull's attack. Mambulls are the highest in health out of all the basic aliens. They do not have an elite variant. Sometimes in Alien Invasion, this alien can deal continuous damage when charging (similar to Xmas Surprise) that can instantly kill you, so watch out. This alien deals melee damage.