- If the event is cancelled, you don’t need to discard any cards. Discarding cards is part of the effect and not a cost.
You dont discard cards... but must you show them before the opponent decides cancelling or not? — DavidDAVE
you declare the target character (step 5 choose a target), then the opponent decides whether to cancel or not (step 6), then you discard however many cards to resolve the ability (step 7). — scantrell24