It is a Kaiju that passed through the inter dimensional portal at the bottom of the ocean and attacked the ctiy of San Francisco. It killed thousands as it destroyed buildings and land marks alike, before being killed by a nuclear bomb deployed by the Military. Unfortunately, this costed many more lives form the blast that finally killed the creature.
Trespasser is the first Kaiju created and sent through the portal to wipe out mankind by its masters, the Precursors. This event was known as K-day, as it marked the first of many Kaiju attacks on mankind.
- Trespasser's alternate name is Axehead.