Appeal // Authority

The value of X is determined only as Appeal begins to resolve. It won’t change later in the turn if the number of creatures you control changes.

You may cast Authority without choosing any target creatures. Creatures you control will still gain vigilance until end of turn. However, if you choose any targets and each of those targets become illegal before Authority resolves, the spell won’t resolve and your creatures won’t gain vigilance.

Once you’ve started to cast a spell with aftermath from your graveyard, the card is immediately moved to the stack. Opponents can’t try to stop the ability by exiling the card with an effect such as that of Crook of Condemnation.

While not on the stack, the characteristics of a split card are the combination of its two halves. For example, Destined // Lead is a green and black card, it is both an instant card and a sorcery card, and its mana value is 6. This means that if an effect allows you to cast a card with mana value 2 from your hand, you can’t cast Destined. This is a change from the previous rules for split cards.

If another effect allows you to cast a split card with aftermath from any zone other than a graveyard, you can’t cast the half with aftermath.

Each split card has two names. If an effect instructs you to choose a card name, you may choose one, but not both.