“Umm, Mr. Dumas... How are you able to create Noble Phantasms?” One of the police officers asked.
The whole group wore nervous expressions. It was their first time speaking to an allied Heroic Spirit face to face. And it was the great writer Dumas. Some of the officers had come in contact with his The Three Musketeers as children. Most of them remembered his works from movies, TV series, and even puppet shows.
Dumas answered the fundamental question from one such “fan” matter-of-factly with a shrug.
“Heroic Spirits can be surprisingly versatile. The stuff you did while you were alive plus the legends is open to an expanded interpretation. In my case, I wasn’t a mage or anything while I was alive, but I did use the money I made to do a lot of things aside from writing.”
Flashing a grin like a child who has succeeded in some mischief, Dumas cheerfully launched into a recital of his past.
“Well, when my buddy Garibaldi said he was going to unify Italy, I decided to give him a little push. I ran loads of weapons in my ship, the Emma. Put out a newspaper, too. In exchange, he made me supervisor of a museum that dug up ruins and relics of the past. Man, did it ever give me a chance to see and touch some fascinating things.”
“Relics... of the past...”
“So, that mixed with a Caster’s ‘Tool Creation’ and ‘Territory Creation’ and anecdotes about my legal messes into a skill. It’s not magecraft; it’s the ‘art’ of faking a Noble Phantasm’s past — its story — and repasting it. The ruins and relics I touched back then might’ve had an influence. A lot of crazy things turned up from around Pompei.”
It seemed that he himself did not fully understand why he had acquired the ability. With the knowledge the world bestowed on him as a Heroic Spirit, however, he was able to perfectly master it.
Dumas chuckled nostalgically and resumed writing on the scroll.

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