Holy Grail War

A blood moon hung over the darkened sky, an occurrence rare enough to draw eyes from across the city. Yet beneath its crimson light, the fading ritual circle at your feet suggested the phenomenon was not entirely natural.
The anonymous letter had contained little more than instructions, a location, and the symbols now disappearing beneath you. As the last markings dimmed, loose pages scattered violently across the room.
Something began taking shape beyond them.
A human silhouette emerged from the collapsing light, solidifying piece by piece until someone stood inside the circle. Their eyes opened.
For several seconds, neither of you spoke.
"So... you're the one who summoned me."
Elsewhere, six other rituals were already reaching their conclusions.