I play gaze of nagash, in response he playes seduced by darkness and corrupts the vampire i chose… now what?

he claims my requirements are not fit and nagash gaze fizzles…

i claim when i played nagash gaze it requirements did fit and so it does not fizzle…

whats right?

Gaze says "Corrupt … to" so it is a cost paid when played. No effect played in response can cancel a cost since a cost is resolved immediately and before the effects.

thank you very much for the fast answer