The creature was measured to be 302 feet tall (92 meters), 2700 tons, with a speed of 7, a strength of 5 and an armor rating of 4. The Trespasser's hide was thick and protective, and presumably could withstand any type of conventional weapon. Trespasser also emits an orange bioluminous glow from inside its mouth.
Trespasser's approach to the city is marked with a 7.1 earthquake, followed shortly by its rise from the water near the Golden Gate Bridge.
It destroys the bridge and everything on it, proceeding to cut a massive path of destruction through San Francisco, Sacramento, Oakland and the numerous surrounding cities. Conventional weapons used by the US military, assisted by the Royal Air Force, did nothing to penetrate the hide of the creature.
The fight against Trespasser lasts for six days before the military would finally resort to using three nuclear missiles to kill it. The three missiles killed Trespasser, but at the expense of Oakland, much of the Bay Area, and all of those living there.
Shortly after its death, the military gathers its remains and put its skull on display for the public. Trespasser's attack is thought to be an anomaly by the general public; however, six months later, a second Kaiju emerges in Manila.
Because Trespasser’s attack occurrs before the formation of the Pan Pacific Defense Corps, when established, the Defense Corps is unable to determine its category class from its corpse.
Once its remains are removed from the area, Oblivion Bay, a graveyard for destroyed Jaegers, is established in Oakland.
Trespasser appears in Pacific Rim: Tales From Year Zero, the prequel to the events of Pacific Rim. The graphic novel was written by Travis Beacham and released June 18, 2013 alongside Pacific Rim: Man, Machines & Monsters.
Scunner and Knifehead use the same basic CG body as Trespasser in Pacific Rim.
According to Travis Beacham, "Axehead" (commonly spelled Axe-Head) was a nickname, referencing the look of the Kaiju, before it was given the name Trespasser.
Kaiceph, the Kaiju that attacked Cabo San Lucas in Mexico, was originally thought to be the remains of Trespasser after the Pacific Rim official facebook posted an image describing it as Trespasser.
According to the prologue of Pacific Rim, Trespasser's attack destroyed the cities of San Francisco, Sacramento and Oakland. However, Travis Beacham states that Trespasser attacked San Francisco, Hayward, San Mateo and San Jose.
Trespasser appears in the Pacific Rim: The Video Game and Pacific Rim: The Mobile Game.
NECA's Pacific Rim Series 3 line will include a Trespasser figure.
Travis Beacham: They aren't sure about Trespasser. It was before the category system, and the nuke that killed it badly damaged its remains.
Travis Beacham: Exactly right. Yep, it's name in the canon is Trespasser. "Axehead" was the look's nickname.