Elfriede operates as an intelligence specialist within the smuggling group Headkeeper, infiltrating the Imperial Capital for solo espionage. She maintains a cool public facade, masking a more vulnerable private self. During her covert work, she uncovers financial irregularities connecting Headkeeper funds to the Imperial Diet, fueling her suspicion of an internal traitor. Her superior, Fritz, then directs her to investigate a closed mental institution, believing it may expose the betrayal.

Inside the institution, Elfriede discovers Mary Bult's role in secret human experiments. Her mission ends when guards capture her before escape. The facility's overseer, Professor Radovaud, subjects Elfriede to irreversible physical transformation experiments, mutating her into a monstrous entity. Though Arnold and Benjamin lead a team that locates her containment capsule, the mutated Elfriede breaks free. She rampages indiscriminately, threatening allies and enemies.

With no hope of reversing her condition, Headkeeper eliminates Elfriede to halt further devastation. In her final moments, she retains enough consciousness to convey critical intelligence about the traitor and Radovaud's experiments to her comrades before succumbing.