How do Isochron Scepter and the Fuse mechanic interact?

Question

The split cards in the expansion set Dragon's Maze contain a new mechanic "Fuse". This mechanic allows you to cast both sides of the spell, a new option for cards of this type.

Isochron Scepter allows you to imprint any instant card with casting cost 2 or less, and then produce copies of that card once per turn.

The interaction of Isochron Scepter and instant split cards is a highly useful one, in that you can imprint a split card providing one side meets the requirements of Isochron Scepter, and then cast either side of the card using Isochron Scepter's linked ability.

The fuse mechanic allows you to cast both sides of the card. How does this mechanic interact with Isochron Scepter? This is relevant so far to Turn // Burn and Far // Away.

Answer 1

You cannot use Fuse.

The reminder text reads "You may cast one or both halves of this card from your hand." The scepter allows you to cast a copy of the card from Exile. That it's not a card may or may not be relevant, but the addition of "from your hand" will surely be present in the rules, so it's pretty clear that Fuse cannot be used here.

As such, it's as if you were casting a regular split card. You can cast either side (even if the mana cost of that side is more than two), but not both.

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UPDATE: The rules have been released, and the "from your hand" is indeed present in them.

702.101a Fuse is a static ability found on some split cards (see rule 708, "Split Cards") that applies while the card with fuse is in a player’s hand. If a player casts a split card with fuse from his or her hand, the player may choose to cast both halves of that split card. This choice is made before putting the split card with fuse onto the stack. The resulting spell is a fused split spell.

702.101b A fused split spell has two sets of characteristics and one converted mana cost. The converted mana cost of the spell is a number equal to the total amount of mana in its two mana costs, regardless of color.

702.101c The total cost of a fused split spell includes the mana cost of each half. (See rule 601.2e.)

702.101d As a fused split spell resolves, the controller of the spell follows instructions of the left half and then follows the instructions of the right half.

Answer 2

This post on Tumblr from a judge makes this pretty clear:

YOU CAN ONLY CAST BOTH HALVES OF A SPELL WITH FUSE WHEN YOU CAST IT FROM YOUR HAND.
Sorry for having to yell there, but people don’t seem to be getting that point, so I have to keep reinforcing it.
Also, you can cast either half of a split card that’s imprinted on Isochron Scepter. Just not both.

As ikegami said, this is because of the clause in the Fuse reminder text that says "from your hand." So after you imprint it, you can use either side like with other split cards, but not both at the same time.

Answer 3

I realise this thread is a number of years old, and I wouldn't normally necro such a thread. However, because I just had the same question myself now with new Split cards about to be released in the Return to Ravnica set in October 2018, I thought to check the Gatherer rulings on Isochron Scepter directly:

http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=413765

18/04/2017

The converted mana cost of a split card is determined by the combined mana cost of its two halves. When you activate the second ability, you may choose to cast either half of the split card, but you may not cast both halves.

It seems that the rules might have changed slightly since the Dragon's Maze expansion, and the current thinking is that you would NOT be able to imprint cards such as Turn // Burn and Far // Away any more, because their CMC (for both halves) would be 5 in both instances.

Edit:

See also:

https://magic.wizards.com/en/articles/archive/news/amonkhet-split-card-rules-changes-2017-04-04

Isochron Scepter can't imprint Far // Away or Bound // Determined.