Can you discard a mystery from your hand to cancel an event an opponent plays or does the mystery have to be discarded from your house? Someone else indicated that it couldn't be "played" on anything other than a house; however, I don't think discarding a card to use its latent ability necessarily qualifies as being played. Thanks in advance!
This refers to "The Sinister Surprise." You must have played the card on your house before you can use it's ability. So you play it on your residence, and then once you have it in play, you may discard it at any time to cancel an event.