Beasts, or Antagonists, shortened as AGs, are the enemies of humanity and first appeared in Cosmic Century 123. They have a caste or hive type of society with a Queen at the top of the hierarchy. High Rank Beasts command over the much more numerous and weaker Low Rank Beasts. EX-Type Zero has the lowest number rank and are extremely powerful. The higher the number rank, the less powerful the Beast is.
They are identified with a rank by humans. Certain infamous ones are given names for easy identification. High Rank Beasts have the biological equivalent of the Human "Core" technology called Nohsim, which is a very compact high yield energy and particle generator, allowing them to emit Personal Shields and project particle attacks. These cores emit a distinctive signature when activated, allowing them to be detected.
Unlike mass-produced Beasts, High Ranks are born in the substitute womb of the Queen Nest. Types 155 and downwards are considered High Rank, being much more powerful physically and mentally, often acting as tactical field commanders.
The Beasts are waging war on mankind. Queens invade a planet, absorb its resources leaving the planet unable to sustain life, and then move on to the next planet. This war has been going on for centuries. At the beginning of the manhwa humanity has been winning, to the point where Anne thinks the end of the war is near, proclaiming a new Human Age. However, a new, very powerful, Queen invades Arin and the Central Order, and quickly launches attacks on other planets and solar systems.
There are major differences between the different ranks, not only in power but in physical appearance, skills, and jobs. Most High Ranks are humanoid both in shape and size, with some exceptions. Even though the High Ranks are often smaller than many Low Ranks, they are incomparably stronger and smarter. In the attack on 7th Space Colony of Arin, a Type 77 is seen leading a group of no.600's, and because of the High Rank's leadership the defending forces are surprised and are nearly overwhelmed.
There are different classes within the different types, especially among High Ranks. This ranking goes Double S, S then A to F (Ep0), with SS being the strongest. In Ramsie's fight with Fang Blade, a Type 2 with 15 years of battle experience, he said that because of Fang Blade's technique and skill he would rather face an inexperienced "EX-Type Zero", meaning that rank generally confers raw power and not always skill. For example, Fear was rated by Dry Leonhard as nearly S-Class despite her average C-Class core, he mused that she needed to be more experience, showing that ranking within the types determines their relative power, therefore, Fang Blade was most likely a S-Class Type 2.
All of the Beasts' technological "machines" are Beasts themselves. This includes all spaceships, launch pads, and plants where Beasts are grown. There are also Beasts that produce jamming signals using Jamil Organs and can even twist visible light to create false images using Chamild Organs. The Beasts' Warp engines are biological as well. Because all technology is biological, the Beast's technological power changes from Queen to Queen. More powerful Queens have more powerful technology. For example, powerful queens that can produce Rank 5 Warp Engine can Warp, or teleport, single units like EX-Type Zeroes from planet to planet. This is demonstrated when Blue Beetle warps to Valtia to rescue her sister Fear in (Ep0 - Ch21).