Ever since split cards appeared in the game, players were attempting to play both halves at once which resulted in well-deserved penalties. Finally, upon release of Dragon’s Maze, the developers gave in and created the special mechanics of Fuse allowing to perform such action legally.
Oracle Text:
Instant, 2U
Until end of turn, target creature loses all abilities and becomes a red Weird with base power and toughness 0/1.
Instant, 1R
Burn deals 2 damage to any target.
Fuse (You may cast one or both halves of this card from your hand.)
A split card with Fuse may be played as a regular split card, i.e.only one of its halves. It continues behaving normally on the stack. Only if you decide to cast a split card from your hand using Fuse do our adventures begin.
Fuse
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.
The first and most important thing to grasp here is that you may only play both halves of a card if that card has the Fuse ability. Split cards without this ability may not be played this way.
The second, no less important thing is that a card may be played with Fuse only from your hand, not from any other zone. When the card is in another zone and you may play it from there, you can only cast one of the two halves regardless if it has Fuse or not.
If Turn // Burn gets Flashback through Snapcaster Mage’s ability, you may cast either Turn for {2}{U}, or Burn for {1}{R}. You may not Fuse them, since the card is played from the graveyard, not the hand.
The old text of Future Sight says “as though it were in your hand”. That’s a blatant lie. Contemporary oracle text is different, and the Library is not the Hand at all. You cannot cast the Fused spell.
708.2b. If a player casts a split card with fuse from his or her hand, in addition to choosing either half as described above, the player may choose to cast both halves, resulting in a fused split spell. Both halves are evaluated to see if the spell can be cast. If either half can’t be cast, then both halves can’t be cast as a single spell.
If the cunning opponent called Blue when Iona, Shield of Emeria entered the battlefield, you may not fuse Turn // Burn, since you may not cast the blue Turn.
If the cunning opponent called Turn for his Meddling Mage, you may cast Burn, but not fuse Turn // Burn, since such a spell has two names, one of which was called for a forbidding effect.
If we do decide to Fuse a split card, we will have to choose targets after putting it on the stack (if the spell is targeted).
Since the word “target” is used twice in Turn // Burn’s text, we may choose one creature as both targets, such as an opponent’s juicy Tarmogoyf.
Even if you choose yourself as the first target for a fused Down // Dirty, you may not return one of the cards discarded this way to your hand, because the target for Dirty must be chosen while casting the spell.
Unlike Down // Dirty, the second effect of Breaking // Entering doesn’t need a target. The creature card is chosen on resolution, so you may choose one of those that were put into graveyard while resolving the first effect.
You may not cast a split card as a fused spell if there are no legal targets for it.
A fused spell has two sets of characteristics and one mana value.
For example, Turn // Burn is both a red spell and a blue spell. If a creature chosen as the first target (for Turn effect) gains protection from red, it becomes an illegal target for the entire spell.
The full cost of a fused spell is the result of adding up the costs of both halves, and the mana value of a fused spell equals to the mana totals of its two mana costs added up, regardless of the colors.
Turn // Burn has mana costs {2}{U} and {1}{R}. In order to cast both halves, you would need to pay {3}{U}{R}. This spell would enter the stack as one with mana value equal to 5, and that means, it may not be cast this way if Gaddock Teeg is present on the battlefield.
If an effect allows casting a card from your hand using an alternative cost, this effect is applicable to a split card with Fuse. In that case this alternative cost replaces both mana costs. With the effect of Fist of Suns ongoing, you may pay {WUBRG} rather than {5UWRR} for Catch/Release. With Counterlash effective, you won’t need to pay at all. Note that Counterlash allows casting a card from the hand, so we may use Fuse.
A fused spell is one spell, not two.
In order to counter a fused spell, only one countering effect is required. Cryptic Command will manage that task.
When copying a fused spell we get a fused spell. Upon applying Twincast we may select new targets for it, but we may not deselect one of its halves to cast just one half of the original card.
When copying a fused spell:
If Arcane Laboratory is on the battlefield, you may easily cast a fused Turn // Burn. Obviously, you won’t be able to cast Turn first, and then Burn as separate spells (you would need two split cards, or Flashback for that).
When casting a split card with Fuse, Extort triggers once. One spell, one trigger, one opportunity to pay {W/B}.
Goblin Electromancer reduced the cost of each instant/sorcery spell by {1}. An independent Turn will cost {1}{U}. Same with Burn — just {R}. The cost of a fused Turn // Burn would be {2}{U}+{1}{R}-{1} = {2}{U}{R}.
When resolving a fused targeted spell, its targets are checked for legality. If all targets of the fused spell are illegal, it is countered. If there are any legal targets remaining, the spell resolves to do as much as it can, with illegal targets set aside.
You cast a fused Turn // Burn, choosing an enemy creature as the first target and your opponent as the second. If the creature becomes an illegal target before resolution, Turn // Burn resolves and deals damage to the opponent. The creature doesn’t fall under the spell’s effect.
Catch // Release only has one target (a permanent for Catch). If, at the moment of resolving the fused spell, that target is illegal, Catch // Release is countered and has no effect at all. Players will not sacrifice any permanents!
According to the rule 702.101d, first, the text of the bottom (left) card has effect, then the text of the top (right) half has effect.
If you choose Tajic, Blade of the Legion as the target for both effects of Turn // Burn, then upon resolving, first Tajic loses all abilities and turns into a Weird, then takes 2 damage which in most cases will be lethal.
Upon resolving Beck // Call, first, the delayed triggered ability is created, then, 4 tokens appear. It leads to giving the controller of Beck // Call a potential opportunity to draw 4 cards.
Ancient Den and Terra Eternal were chosen as targets for Wear // Tear. When resolving, Wear // Tear first fails to destroy the land, then successfully destroys the enchantment. A fused spell may not be resolved in the opposite order.
Neither player has priority while a spell is resolving, so, neither player may sneak in a spell between the effect of two halves of a fused spell.
If a player draws an instant card while resolving a fused Toil // Trouble, he may not play it.
If the drawn card is the first card drawn this turn and has Miracle, the player may reveal it, but the Miracle trigger will enter the stack only after Toil // Trouble finishes resolving.
An interesting situation for dessert:
The cunning opponent enchants our Kitchen Finks with one -1/-1 counter on them with his Runner’s Bane. We cast Give // Take and choose the Ouphe as both targets. What happens on resolution?
First, the Finks get three +1/+1, eventually growing in size up to 5/4. Then, three +1/+1 counters are removed from them and you draw three cards. Kitchen Finks keep their -1/-1 and the aura.
Why didn’t +1/+1 and -1/-1 counters cancel each other out, and the aura did not fall off when Kitchen Finks got huge? Thing is, SBA aren’t performed all the time, but at very specific moments of time. When SBA were checked just before a player would get priority, the state of the game was trivial — one sole counter on the Ouphe, and an aura enchanting a due creature.
We have already discussed Turn to Frog in detail, including the +1/+1 counters on the creature (they modify the base P/T values and increase the Weird’s stats), and all about animated Gideons (damage prevention won’t go anywhere!). The Turn effect is mostly identical to that of Turn to Frog, you just need to swap “Frog” for “Weird”.
If you resolve a fused Turn // Burn that targets one creature for both effects, first that creature turns into a Weird, then takes 2 damage. In some cases, this damage won’t be lethal.
- ⇑ 708.7 Each split card has two names. If an effect instructs a player to name a card and the player wants to name a split card, the player must name one of those names and not both. An object has the chosen name if one of its names is the chosen name.
Translated by Witas Spasovski
If an opponent controls Counterbalance and you know for sure that it is safer to cast a fused spell with mana value=3, than a Tear with mana value=1, then, to play Wear // Tear as a fused spell, you need two legal targets: an artifact and an enchantment. You may not target Counterbalance with a fused Wear // Tear without another target.