Let’s talk about Aftermath
Right, so... Aftermath. That’s a thing now, so we’re going to need to have a talk about it. Time for some Q&A:
(These answers have been verified as correct by Eli Shiffrin, Magic Rules Manager on 3 April 2017. The answer to the final question was corrected to reflect an upcoming change in Amonkhet.)
Q: What the hell is this thing?
A: It’s a split card.
We’ve seen split cards before in Invasion, Apocalypse, Dissension, Planar Chaos, and Dragon’s Maze.
Q: So why does it look different from other split cards?
A: Because it works differently from other split cards. When you want to cast a traditional split card like Life // Death, you choose one of the two halves to cast and just pay the costs for that half and follow the instructions for that half. (If the split card has fuse and you’re casting it from you hand, you can also choose both halves.) With a split card with Aftermath, you can only cast the top/left half from your hand (or from any other zone than the graveyard). The right/bottom half can only be cast from the graveyard.
Despite the different layout of the Aftermath cards, they’re split cards in every way and could be functionally printed with the same layout as a traditional split card without changing their functionality. It’s the Aftermath ability on the right/bottom half that makes the difference.
Q: So what does the Aftermath ability on the right/bottom half actually do?
A: Aftermath means two things. First of all it means “You may cast this spell from your graveyard, but not from anywhere else.” This applies only to the half of the card with Aftermath. It also means “Exile this card instead of putting it anywhere else any time it would leave the stack.” Again, this only applies to the half of the card with Aftermath.
Q: Ok, so do I have to have cast the top half to be able to cast the right half from my graveyard?
A: No. You can cast the right half of a card with Aftermath from your graveyard no matter how it got there, be it through discard, milling, or the top half resolving or being countered.
Q: When can I cast a card with Aftermath from my graveyard?
A: Any time you could cast a spell of that type. Lead is a sorcery, so you can only cast Lead from your graveyard when the stack is empty during your main phase (or at other times if an effect like Hypersonic Dragon or Quicken give you permission to do so.)
Q: How can I cast both halves of an Aftermath card at the same time?
A: You can’t. There is (currently) no way to do so. What you can do is cast the bottom/right half from your graveyard immediately after the top half resolves. (See previous quertion re: timing.)
Q: What happens if give an Aftermath card in my graveyard Flashback (Snapcaster Mage / Past in Flames) or otherwise get permission to cast it from there? (Jace, Telepath Unbound)
A: Then you can cast either half from your graveyard, but not both. (See previous question.) When a split card gains flashback, each half gains a separate flashback cost. If you targeted Destined // Lead with Snapcaster Mage’s trigger, then Destined will have Flasback 1B and Lead will have Flashback 3G until end of turn. When you cast the card this way, it will be exiled instead of returning to your graveyard when it finishes resolving.
Q: But if I can cast both halves from my graveyard, then why can’t I cast both at the same time?
A: For the same reason that you can’t cast both halves of a normal split card from your hand at the same time. Spells are cast one at a time, and you have to pick one half of the card or the other to cast. When you cast the card it moves to the stack and is no longer in the zone you cast it from.
Q: What about the Expertise cycle? Can I do anything weird with Aftermath cards there?
A: Maybe! Aftermath cards work the same way with the Expertise cycle as normal split cards do, with the exception that the right half can’t be cast from your hand and thus can’t be cast off of an Expertise spell.
What this will mean is that, if there’s an Aftermath card whose top half has a higher converted mana cost than its right half, you’ll be able to cast that more expensive top half of the Aftermath card from your hand as long as the right side’s cost meets the CMC criteria of the Expertise spell. (For example, if Destined cost 3B and Lead cost 1G, which they don’t, you could cast Destined off of Kari Zev’s Expertise because one of the card’s CMCs is 2 or less.) ^ Nope. None of this is correct as of Amonkhet’s release. See below. ^
Update from Eli Shiffrin, Magic Rules Manager: “Previously, we played a delicate dance when asking about converted mana cost. Sometimes Destined//Lead's CMC is most like 2: Goblin Dark-Dwellers can target it. Sometimes it's more like 4: Transgress the Mind can blorp it. Sometimes it's more like 6: Dark Confidant dings you for 6 if you reveal it. This rewards players who dig into the rules and figure that out, but it baffles a lot of people, too. So now, it's simple: If Destined//Lead isn't on the stack, it has a converted mana cost of 6. Destined on the stack has a CMC of 2, and Lead on the stack has a CMC of 4, but Destined//Lead, any time it's not one or the other, has CMC 6.”