". . How many of the ‘bullets’ inside you are left?”
He aimed to rattle his opponent by saying something that would confuse him.
He did not know his Servant “Watcher’s” identity, but its unique ability to perceive everything that occurred in the city while it was summoned made it like a fantastical surveillance system.
According to the information he had been able to gain through its ability . . . the vampire known as Jester possessed a number of cores that he called “bullets” and was able to rearrange his entire body, including his soul, by switching between them.
His Spirit Origin as a mage seemed to have been destroyed by Assassin, but Sigma did not know the details because Watcher had not been summoned at the time.
“. . . What?”
The effect of Sigma’s provocative suggestion that he knew Jester’s secrets was simple, but immediate.
Jester wiped the expression from his face and confronted the already-expressionless Sigma with a masklike face.
“. . .?”

Fate/Strange Fake: Volume 5, Interlude ("Mercenary, Assassin, Vampire II")