Forum:Ally of justice catastor vs. Disciple of the forbidden spell

Ok so i was wondering ally of justice catastor says: At the start of the Damage Step, if this card battles a non-DARK monster: Destroy that monster immediately (without damage calculation). But Disciple of the forbidden spell says:When this card is Summoned, declare different Monster Card Attributes equal to the number of "Disciple of the Forbidden Spell"(s) in your Graveyard. If this card attacks a monster that has a declared Attribute, destroy the monster with this card's effect without applying damage calculation. If i call dark and attack castastor who would die?