Battle of the Breach
In a last ditch effort to protect the Breach, the Precursors create Slattern. Acting as additional offense for Scunner, and Raiju, the Slattern attacks Striker Eureka. On the offensive, Slattern pushes the Jaeger away from the Breach, damaging it armor with its triple-crowned tail.
When Striker Eureka's Sting Blades slice through Slattern's hide, Slattern is forced to back off and calls for aid from its only surviving partner, Scunner. Poised to destroy Striker Eureka, Slattern and Scunner rush to tear the Jaeger apart and are caught in the detonation of the thermonuclear bomb. While Scunner is killed, the explosion severely wounds Slattern.
It jumps in front of Gipsy Danger in an effort to block its path to the Breach. Pilots Raleigh Becket, and Mako Mori abandon the half corpse of Raiju and pull Slattern over the ledge into the Breach. Using the nuclear turbine, Gipsy Danger burns through Slattern's internal organs, killing it. Slattern's body allows Gipsy Danger to pass through the Breach and enter the Anteverse.
Pacific Rim: Aftermath
When Jake Pentecost breaks into Giovanni Capello's mansion, he decides to use the stolen Drift core from Striker Eureka that survived the Jaeger's destruction in the nuclear explosion. Ghost drifting with the memories of his father, and Chuck Hansen, Jake witnesses his father's final moments against Slattern, and his unspoken apology to Jake.
Pacific Rim: The Black
When pilots Taylor and Hayley Travis search for the missing Kaiju Boy, Atlas Destroyer's A.I. picks up on the skeletal remains of multiple Slattern alongside multiple Leatherback, and Mutavore scattered in a boneyard.