For your example for SoF, when it blocks you have two options. Either you must let the opponent discard a card from your hand or you choose let it withdraw your heros. If you let it withdraw your heros, you will then have special initiative to negate SoF because your heros are being removed from battle. However, if there is a card that does something like discard from your hand AND removes your hero from battle, you have to complete its ability and discard the card before you have the option negate it.
