In a nutshell:
- Double faced cards have a second card face instead of a Magic card back.
- Each face of a double-faced card has its own set of characteristics.
- Everywhere except the battlefield, the front face is the only face the game looks at.
- On the battlefield, whichever face is up determines what characteristics the permanent has.
- Except: The converted mana cost of a double-faced permanent’s back face is calculated as though it had the mana cost of its front face.
- A double-faced card enters the battlefield with its front face up, unless an effect puts it onto the battlefield ‘transformed.’
- The term ‘transform’ refers to the action of turning over a double-faced card so its other face is up.
- A double-faced card whose front face is up will transform to its back face and vice versa.
- Non-double-faced cards can’t transform.
- Transforming a permanent doesn’t change its status. If it was tapped before, it will still be tapped.
- If an ability wants to transform a double-faced card, but that card has transformed since that ability was put onto the stack, the ability’s instruction to transform it is ignored.
- Double-faced cards can exist on the battlefield face down, for example if they’re manifested. A face down double-faced card can’t transform. Similarly, a face up double-faced card can’t be turned face down.
A: Nothing interesting. The legend rule doesn’t apply because Liliana, Defiant Necromancer isn’t legendary. The planeswalker uniqueness rule doesn’t apply because Liliana, Heretical Healer isn’t a planeswalker. Even though it’s the same storyline character, and even the same card, the game doesn’t have a problem with it.
A: Anywhere except the battlefield, the back face of a double-faced card is ignored when determining the card’s characteristics. This means the game won’t be able to see that Nissa is a planeswalker if you turn the card over and Tarmogoyf is a 1/2.
A: Transform doesn’t just refer to the act of turning a card from its front face to its back face, even though that’s the only way it’s used in Origins. Gideon is a human, and it’s double faced, so it transforms into its pre-spark form. There’s nothing telling us to take Gideon’s loyalty counters away here, so they remain, even though they don’t do anything now. Kytheon is still the same permanent, it still has the same controller, and it’s still a creature, so it’s still attacking (although, not being a wolf or werewolf, its combat damage will be prevented. Notably, Kytheon being the same permanent also means it is still affected by all the same effects that were applying to it earlier. This means that it’s still 4/4, it’s still indestructible, and all damage that would be dealt to it is still prevented. It isn’t still a planeswalker, though. That clause isn’t changing or adding card types; it just exists to let Gideon keep its old types after the ability changes its type to creature.
Note: If Kytheon’s “transform me” ability resolves sometime later, it will exile Kytheon, which means all the counters on it will cease to exist. It will return to the battlefield with only 3 loyalty counters on it.
A: Grizzly Bears will have 3 damage marked on it and will die as a state-based action. This will cause Copy Enchantment/Skin Invasion to trigger. After this, the game will put Copy Enchantment into Nicole’s graveyard as a state-based action. When the trigger resolves, Nicole will be instructed to return Copy Enchantment to the battlefield transformed. Copy Enchantment doesn’t have a back face, so it can’t be “transformed,” rendering this instruction impossible. Copy Enchantment will remain in Nicole’s graveyard.
A: No. Treasure Map is tapped when the instruction to transform it is carried out. Transforming a permanent doesn’t change its tapped or untapped status, and the ability that transforms it doesn’t say it untaps it either, so this permanent will still be tapped after it transforms.
A: Clone isn’t a double-faced card, so it can’t transform. You won’t be able to carry out that instruction, so it will just stay an Elusive Tormentor.
Note: Similarly, if you Clone an Insidious Mist, it won’t be possible to transform that into Elusive Tormentor.
A: You can double activate the ability the way you described, but you won’t be satisfied with the result. If an ability wants to transform a double-faced card, but that permanent has transformed since that ability was put onto the stack, the instruction to transform the double-faced card is ignored.
A: No. The converted mana cost of a double-faced permanent’s back face is calculated as though it had the mana cost of its front face. Even though you can’t see it without turning the card over, Perfected Form’s converted mana cost is 4.
A: Yes. Clone isn’t a double-faced card, so its converted mana cost is converted the old-fashioned way: by looking at its mana cost. Except that Perfected Form doesn’t have one. The converted mana cost of this Clone is therefore zero.
A: Unfortunately, you can’t keep it around. This is where the rules for this get kind of weird. Perfected Form’s converted mana cost is 4 because there’s a rule that says when you’re determining the converted mana cost of the back face of a double-faced permanent, you calculate it using the front face’s mana cost. There’s no similar provision for determining the mana cost of a double-faced permanent, so Perfected Form just doesn’t have one. Because it doesn’t have a mana cost, paying that cost is an impossible action, and you’re forced to sacrifice it.
A: A double-faced card has no back face. While it’s possible for them to exist face down on the battlefield if they enter that way (for example, by being manifested, it’s not possible for a face up double-faced card to be turned face down. Ixidron’s ability will not affect Delver of Secrets, and it will remain a face up, untransformed, 1/1 creature.
A: No. Although the physical actions of transforming a permanent and turning a face down permanent face up are the same, these are distinct game actions, and one will not trigger things that look for the other.
Note: It’s possible for a Hinterland Logger to trigger Deathmist Raptor, but it would have to be on the battlefield face down first. This can happen, for example, if it’s manifested.
Q: How do double-faced cards work in draft?
A: Ordinarily, it’s against the rules for a player to show cards in a pack to the other drafters. Obviously, double-faced cards make this rule impractical to follow, so it’s suspended in their case. Both faces of a double-faced card may be revealed at any point during a draft. For further information on applying this rule, see this tip by Josh Stansfield.
Q: Is a double-faced card’s transform trigger generally considered detrimental? In other words, should a player get a Warning for missing one of these triggers?
A: The general consensus is that the ability that transforms a card into its front face is detrimental, whereas the ability that transforms it into its back face is not. In most cases, this is pretty non-controversial, but there’s a few places where it’s questionable, like Mayor of Avabruck in a deck that’s mostly Humans. Remember that in order to remain consistent, the decision of whether a triggered ability is generally detrimental should not take into account the current game state or strategic concerns.