The Heroic Spirit had declared his own true name. The contract had not yet been sealed, so it had not been telepathy, but Faldeus was certain that the introduction had reached no ears but his own. The whisper had actually stirred only a single point in Faldeus’ brain. It had felt almost like a curse seeping into his guts.
“So long as you retain your faith, I shall be your shadow.”

Fate/Strange Fake: Volume 2, Chapter 5 ("Day 1, Dawn")