My opponent declares Lulu, Loyal Hollyphant to be attacking with Greatsword of Tyr. In response, I murder Lulu. Does the Greatsword's "tap up to one target creature" effect still resolve?
1 Answer
Yes, the ability will still resolve. Actually you can't respond to attackers being declared, since declaring attackers does not use the stack (CR508.1). You can respond to the trigger from Greatsword being put on the stack after attackers are declared, but removing the source of the ability once it has been triggered/activated does not prevent that from resolving (CR113.7a). Emphasis in the rules quotes mine.
508.1 First, the active player declares attackers. This turn-based action doesn’t use the stack. To declare attackers, the active player follows the steps below, in order. If at any point during the declaration of attackers, the active player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 727, “Handling Illegal Actions”).
113.7a Once activated or triggered, an ability exists on the stack independently of its source. Destruction or removal of the source after that time won’t affect the ability. Note that some abilities cause a source to do something (for example, “Prodigal Pyromancer deals 1 damage to any target”) rather than the ability doing anything directly. In these cases, any activated or triggered ability that references information about the source for use while announcing an activated ability or putting a triggered ability on the stack checks that information when the ability is put onto the stack. Otherwise, it will check that information when it resolves. In both instances, if the source is no longer in the zone it’s expected to be in at that time, its last known information is used. The source can still perform the action even though it no longer exists.