The being you saw behind me was the actualization of one of those masks. I'm not entirely sure what it is about the Dark Hour that allowed us to manifest it, but by accepting death and learning not to fear it, we can evoke those persona.

[ He mimicked a gun and placed his fingers at his temple. ]

The Evoker acts as a sort of medium to do that, but I don't think it's actually required at all times. There those I know who didn't need one.

[ Aigis came to mind, whose evoker was built in, and Koromaru, who used one built into a collar. Takaya used nothing at all. So there was a way to summon them without using one. If Minato couldn't get his back, he would like to figure out an alternative way, to help better protect himself and those here. ]