If Bazdilot wins this War, Scladio will be unstoppable. Once the combination of the ‘mud’ and crystals spreads to the Scladio Family’s other mages, they’ll become even more powerful than they already are. If that happens, they’ll be a check on the Clock Tower and the Holy Church... but government control will no longer be possible. Having gone over his various concerns, Faldeus made a decision.
I will arrange for Bazdilot to disappear during this Grail War. But that alone won’t be enough.
“There is no one else here,” he murmured. “I would like to speak directly. Will you agree to that, Assassin?”
Every light in the room went out. All about him, darkness ruled.
It had a different quality from ordinary darkness. Faldeus felt a pressure as if the shadows around him were living, crawling things. A shiver ran down his spine.
Before he had a chance to activate a night vision spell, a voice called out from behind him.
“...Speak that which troubles thee.”

Fate/Strange Fake: Volume 3, Chapter 9 ("Day 1, Evening")