Kaiju (Pacific Rim)

Kaiju is the designation given to a group of titanic-sized, silicon based organisms used by extradimensional beings called the Precursors to begin colonization of a planet.

Little is known about Kaiju anatomy, other than that they have skeletons like Earth's vertebrates, have two brains, and that their body fluids are ammonia-based, extremely acidic, have a vivid blue coloration and are highly toxic to Earth's environment. The appearance of a Kaiju varies wildly between individuals, and although it's clear that they are genetically engineered by the Precursors, it isn't known whether each Kaiju represents a unique individual or one of a variety of species, subspecies or phenotypical variants. At least one Kaiju (Otachi) is able to reproduce on its own. It isn't known if all of them share this ability.

The intellectual capacity of an individual Kaiju is hard to tell, but it is known that they possess a hive mind of sorts, are able to devise battle strategies and concentrate their attacks on urban areas. However it appears that the higher the category of Kaiju, the more intelligent it gets. Their bodies serve as environment for a crustaceanoid parasitic creature known as the Kaiju Skinmite, which needs high quantities of ammonia to live.

History
The Kaiju were created by the Precursors with the plan plan that they could wipe out humanity so the precursors could colonise Earth. The Precursors created a breach in the pacific ocean which was portal between our universe and the Anteverse (their universe). The Precursors then started sending Kaiju through to attack earth. They attempted this in the Triassic era but the co2 levels were too low but since humans had been pumping co2 into the atmosphere the conditions in present day were just right.

Human-Kaiju war
The First Kaiju they sent through was Trespasser. Trespasser was extremely tough (likely because he was the first one). Trespasser rampaged and destroyed three cities (San Francisco, Sacramento and Oakland). Before it was finally killed by three nukes. The humans thought this was a one off event and moved on. However six months later another Kaiju named Hundun attacked Manilla. Hundun was also killed by a nuke. A kaiju called Kaiceph then attacked Cabo San Lucas and these Kiaju attacks continued causing the birth of the Jaeger program.

Appearances

 * Pacific Rim (2013)