From the body horror parasites of Halo to the original pixel art aliens in Space Invaders, video games have played host to a variety of dangerous alien races. These games often depict one of humanity's biggest collective fears: that of being wiped out completely. The aliens in these games are often stronger, highly advanced, and ready to kill or enslave the entire human race.

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Often shown invading Earth or other human settlements, many of these games are classics in the sci-fi genre and offer players the chance to wage galactic wars, defending humanity to the last. Each of these races poses a huge threat to the continued existence of those in-game, becoming the ultimate foes in humanity's fight for survival.

10 Shu'ulathoi

Half-Life 2

• Alien Type: Grub-like Psychic Beings
• Purpose: To Control Other Races

As part of the multidimensional collective, known as The Combine, the Shu'ulathoi are rumored to be the ruling species of this mysterious and vast empire. Also known as Combine Advisors, these grub-like beings are extremely powerful and can use telepathic and telekinetic powers.

While not individually fast or strong, their abilities allow them to communicate and lead the other armies of the Combine that would go on to successfully invade Earth. They are also able to use their telekinetic powers to great effect and can destroy buildings with little effort. Shu’ulathoi seem very alien to human eyes, looking much like larvae, they have no features or limbs, and require cybernetics to see and touch.

9 Ethereals

XCOM

• Alien Type: Frail and Thin Aliens With Powerful Psychic Powers
• Purpose: To Subjugate Other Races Into Their Empire

Taking many forms, but all under the control of the Uber Ethereal, the aliens of XCOM are known as X-Rays by the soldiers who fight them. Initially, these extraterrestrial lifeforms enjoyed technology that far outclassed their human opponents, but humanity quickly caught up, using alien plasma technology to create their own weapons.

The X-Rays come in various forms, from the traditional-looking alien Sectoids to the human-looking Thin-Men, and the large and powerful Mutons. All are controlled by the Ethereals, though. These psionic aliens lead and control all other species, and while they are physically weak, their mind powers far outstrip other races, making them incredibly dangerous foes.

8 The Invaders

Space Invaders

• Alien Type: Multi-Dimensional Marine-Life Like Invaders
• Purpose: To Conquer and Kill Humanity

Taking the form of pixelated marine life, little is known about the mysterious Invaders from the original sci-fi video game. Hailing from the Invader Dimension, this destructive race made its way into the Milky Way and attempted to conquer Earth. There are various forms of Invader, with some taking the shape of either a crab, octopus, or squid.

With ruthless tactics, the invaders managed to destroy much of human civilization with their constant waves of attack. Although simple in appearance, the Invaders were very successful in their goals and forced humanity to find a new home.

7 Thargoids

Elite Dangerous

• Alien Type: An Insectoid Species
• Purpose: To Farm Resources From Worlds and Protect Their Borders

This popular space flight simulation game allows thousands of players around the world to fight in a joint galactic war against the dangerous Thargoids. These highly advanced aliens operate vast spaceships of a biomechanical nature that patrol and fiercely defend their regions of space. They are extremely territorial and refuse any kind of peace with their interstellar neighbors.

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Humanity has been waging war with the Thargoids for hundreds of years now, with the second major conflict starting in the 34th century. Although a powerful race, their main goal is to mine a planet for its resource wealth, rather than conquest. The Thargoids employ devastating weaponry, from EMP weapons to combat drones and caustic missiles, that eat away at an enemy's spaceship.

6 Chimera

Resistance

• Alien Type: Monstrous Reptilian Warriors
• Purpose: Reconquer Earth and Mutate The Population Into Hybrid Chimera

The Chimera are an ancient race of aliens that had previously occupied Earth in prehistoric times. Reemerging in the 20th Century, they look to reconquer the planet by killing or infecting the human race. The ancient Pure Chimera uses biological warfare in the form of a virus that was released from a meteor in 1908. Quickly spreading, this virus mutates living creatures into hybrid Chimera, who then fight for their side.

The Chimera were a highly advanced race and were able to successfully invade much of the world in a very short span of time. They attempted to terraform the planet, to change the climate to suit themselves. Although powerful, their weakness was their reliance on the hive mind control of the Pure Chimera. Taking this away, humanity succeeded in overthrowing the invading race.

5 Strogg

Quake

• Alien Type: Cybernetic Warriors
• Purpose: To Harvest Living Tissue To Repurpose Into Food and Other Strogg

These cybernetically augmented alien creatures are the main antagonists in both Quake 2 and Quake 4 and have been waging a long war against humanity. The origins of the species are unknown, but they rely heavily on technology to further their numbers and enhance their firepower. The Strogg harvests the bodies of other creatures, using them as the basis to create more of their kind. These deformed cybernetic monstrosities are then sent to war.

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The Strogg were originally thought to be humanoid in appearance, but their ancient forms are long forgotten. As their society descended into war and augmentation, their sole goal was now the gathering of Stroygent, their only source of food and energy, collected from living beings. The Strogg have several variations, all designed for a different aspect of war. They are ruthless killers and powerful foes.

4 Bugs

Helldivers 2

• Alien Type: Large Insectoid Creatures
• Purpose: To Spread and Grow Their Numbers

The endless swarms of giant bugs in Helldivers 2 represent one of the greatest dangers for humanity in the game. These rampaging creatures may not have the technology, but they have the numbers. They are somehow able to travel through space and infest different worlds. Growing extremely quickly, the bugs can overrun a planet before the threat is even identified.

The bugs can evolve into different species, from the Tank types, which include Behemoths and Impalers, to the Infantry species, which include Stalkers and Elites. One of the most dangerous forms is the Hive Lord, which are giant worm-like creatures that burrow through a planet’s crust, creating new hives for the bugs. If these massive bugs aren’t stopped, they will continue to spread throughout the galaxy, destroying planets as they go.

3 Metroids

Metroid

• Alien Type: Fast-Growing Bio-Engineered Creatures
• Purpose: To Fight Against the X Parasites

Genetically engineered by the alien Chozo race to fight against the X Parasites, the Metroids are the main antagonists of the Metroid series. Appearing in many forms, they start their life as jellyfish-like creatures that eventually grow into more advanced variations, including Evolved Metroids and Queen Metroids, which is the only variant that can lay eggs.

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Series protagonist Samus Aran would eventually see the extinction of their race, although to save her from the X Parasite, Metroid DNA was used on her, making her part-Metroid and technically the last in the universe. Metroids are apex predators, capable of consuming other species and absorbing their energy and even their abilities.

2 The Flood

Halo

• Alien Type: Parasitic Organism
• Purpose: To Grow and Infect All Sentient Life

One of the most successful game series in history, Halo revolves around the war between humanity, the multi-race alien alliance known as The Covenant, and the parasitic species, The Flood. With their natural desire to infect all sentient life, The Flood pose a threat to all living things and are responsible for the mass death of the ancient Forerunners.

The Flood are the reason the Halo superweapons were created in the first place, as they could infect all life in the galaxy if they weren't stopped. The Flood forms a hive mind, making it very difficult to stop. When an infection consumes enough biomass, it forms an even more intelligent version known as a Gravemind, which can lead to The Flood fighting with even greater coordination and efficiency.

1 Reapers

Mass Effect

• Alien Type: Giant Galaxy Spanning AI Machines
• Purpose: To Cull Organic Life Every 50 Thousand Years

These ancient, highly intelligent machines pose not just a threat to humanity, but to all life in the galaxy. The Reapers were created millions of years ago by the first sentient race in the Milky Way, the Leviathans. Returning every 50 thousand years to destroy all advanced life, they leave only primitive races alive to inherit the galaxy for the next cycle.

The Reapers are close to unstoppable, as huge sentient star ships they repurpose alien races into mindless husks to fight for their cause. In the game, it is only the combined efforts of every advanced race in the galaxy, and the hero, Commander Shepard, that can stop the Reaper threat. Few other aliens in video game history would be able to take on the Reapers and survive.

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