Secret of Pedigree

Helm of Hidden Infidelity. The Noble Phantasm of Saber of “Red,” Mordred. She hid her face with a helmet given to her as a set with a suit of armor by Morgan in order to prevent King Arthur and his subordinates from learning of her true identity.
It's a little like a simplified version of “For Someone's Glory: Not For One's Own Glory” from Fate/Zero. The condition to negate the effects of this Noble Phantasm is solely the act of her removing her helmet on the battlefield, so it will continue to hide her stats even if she walks around normally with her face unhidden. I understand it seems like a bit of a lame excuse, but walking through the streets in a suit of armor only works in a Fantasy RPG world, so please bear with it.
Perhaps due to having being enchanted by Morgan, both the helmet and armor are quite sturdy in terms of defense as well. Furthermore, “Clarent Blood Arthur: Rebellion Against My Beautiful Father” cannot be used until the helmet is removed. As a result, Mordred keeps it almost always removed after she first takes it off the time.
This is a bit of a digression, but the helmet isn't placed down anywhere when it's off, but instead is inserted into the armor (the reverse is also possible). I found the scene where the protagonist of a certain Sci-Fi Horror TPS Game equipped their helmet to be really cool, so I fervently requested it of Konoe-san1. Even if the author was satisfied with it, it was probably a huge annoyance to him. Sorry.

Fate/Apocrypha material: Fate/Apocrypha Encylopedia
Translator's Notes
  1. ^ The illustrator.