"So, kid. What kind of Servant is he, that guy?"

Rider asked Waver, but the small Master shook his head, dumbfounded.

"... I don't know. I simply can't tell."

"Whaat? You're a Master, aren't you? His strong and weak points should be visible to you, eh?"

As a Master who has made a contract with a Servant, it is possible to read out the status of a Servant with powers of clairvoyance. This is a unique ability granted by the Grail that has summoned the Heroic Spirits. This doesn't work for the fake Master that is Irisviel, but Waver, rightful Master of Rider, is capable of seeing through the abilities of the other Servants and compare them to those of Rider, to guide him as efficiently as possible in battle situations. In fact, Waver already had a clear understanding of the faculties of Saber, Lancer and Archer. But—

"I said I can't see it! That black guy is definitely a Servant... But I just can't read out his stats!"

Rider frowned in suspicion at Waver's confused explanation, and took a new look at the black knight.

- Fate/Zero: Act 4, Part 2