Zed Theory
I have a theory about a potential connection between Zed and Nocturne. The Black Box that Zed opened, contained Nocturne. Long after he was banished from the Kinkou Monastery by Master Kusho, he came back to the temple. When Zed was alone with his master, Zed screamed in pain. The reason for that could have been that Nocturne gave him illusions, that he was attacked (by Nocturne himself or his master). So, Zed fought back and killed Kusho, either because he thought he was Nocturne due to the illusions or because he thought that Kusho tried to killed him (probably again due to Nocturne's illusions).
Some clues that prove (a part of) this theory:
>Nocturne's Lore: "For centuries the practice of "shadow magic" was all but forbidden across Runeterra"
>Zed's Lore: "Shadows enveloped Zed's mind, feeding his bitterness with contempt for the weak, and hinting at an ancient, dark magic.
