And Berserker was slowly vanishing into thin air. Even the sound of it was disappearing. The “pressure” it exerted, however, remained in workshop.
This is different from the concealment Filia performed in the city earlier. Even I can’t see it.
Can this Heroic Spirit turn invisible under its own power...?
Haruri gulped. It was coming home to her that she had made a contract with a shocking Heroic Spirit.

Fate/Strange Fake: Volume 4, Chapter 12 ("Day 2, Morning")