User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-4802891-20170404162419/@comment-4802891-20170413145119

One more hint to help you all :

The Noble Phantasm of this Servant is a set of very similar weapons, like Jack the Ripper's knives. Like these, they are relatively weak (rank D or C), but when used by the "right" Heroic Spirit, it gets ranked up to B. Releasing the True Name of this Noble Phantasm allow all Heroic Spirits in the Servant to acts separately for a short period of time, all wielding their favored weapons. As you can see, using it also reduces Buster damage, which means it get rid of the Mad Enhancement for a while because the Servant isn't Legion-like anymore.

In the case of a successful, non-jammed summoning, the NP would only be C+ because only one Servant would try to emulate everyone's skill with a weapon by wielding them all at once telepathically (Nobunaga-style).