Magic introduced transforming double-faced cards (DFCs) in the original Innistrad, making these the earliest DFC design. As more sets have included transforming DFCs, the symbols indicating the front and back faces have changed a few times.
|SET||FRONT SYMBOL||BACK SYMBOL|
|Innistrad block & Shadows Over Innistrad||sun||crescent moon|
|Magic: Origins & Core Set 2019||modified Planeswalker icon||full Planeswalker icon|
|Eldritch Moon‡||full moon||stylized Emrakul|
|Ixalan & Rivals of Ixalan||compass rose||land icon|
‡ Ulrich of the Krallenhorde // Ulrich, Uncontested Alpha uses the sun/crescent moon symbols despite being from Eldritch Moon.
I appreciate that Magic's talented designers wanted to flavorfully show players which face was which. However, here we are years later, needing a chart to keep track of what means what. This is, as the kids say, "not cool."
But enough about that! What's the cool stuff transforming DFCs can do? As it turns out, we can split transforming DFCs into a few different subclasses. First, let's look at the rules that govern all transforming DFCs. Then we can dive into what differentiates "regular" transforming DFCs from daybound/nightbound and disturb cards.
It Happens to Everyone
Anywhere but the battlefield or the stack, transforming DFCs have only the characteristics of their front face. Practically, this means I can't Crumble to Dust my opponent's Azcanta, the Sunken Ruin and exile all of the Search for Azcanta // Azcanta, the Sunken Ruins in their deck.
Generally, when a player casts a transforming DFC, they put it on the stack with its front face up. However, if something lets them cast it "transformed," they put it on the stack back face up. The spell has the characteristics of whichever face is up.
A transforming DFC's mana value is calculated using its front face no matter where it is. A transformed Delver of Secrets // Insectile Aberration has a mana value of 1; Dorothea, Vengeful Victim // Dorothea's Retribution has a mana value of 2. However, a copy of the back face of a transforming DFC permanent or spell has a mana value of 0.
A transforming DFC that wasn't cast generally enters the battlefield with its front face up. For example, if my opponent Ephemerates my Insectile Aberration, it has to re-enter as a Delver of Secrets. I'd have to transform it again.
When a transforming DFC transforms, it's still the same object. Any auras, effects, and/or counters remain on the permanent. The exception, of course, is when an instruction tells us to "exile it, then return it transformed" on something like Jace, Vryn's Prodigy // Jace, Telepath Unbound. In that case, the DFC would leave and then return to the battlefield. Since it's a new object, it doesn't have any of its old auras, effects, and/or counters.
Only permanents represented by transforming DFCs can transform. If something tells a player to transform something that isn't represented by a transforming DFC, nothing happens. For instance, if I Clone a Huntmaster of the Fells // Ravager of the Fells, my Clone-Huntmaster won't ever transform.
Finally, if a permanent would transform, but its other side is represented by an instant or sorcery card face, nothing happens. The game really doesn't want instants or sorceries on the battlefield, for obvious reasons.
A Little Weirdness
A couple of paragraphs ago I said that only permanents represented by transforming DFCs can transform. If one transforming DFC is a copy of another, it can still transform... but the transformation won't do much.
Let's say I cast Mirrorhall Mimic // Ghastly Mimicry and have it copy Huntmaster of the Fells // Ravager of the Fells. My opponent casts no spells on their turn, then passes back to me. At this point, Huntmaster transforms into Ravager, and the Mimic-Huntmaster transforms into... Huntmaster.
Well, our Mimic-Huntmaster is represented by a transforming DFC, so it can transform. However, Mimic's copy effect only copied the face of Huntmaster that was currently face up. While it physically transforms, it still has all the characteristics of Huntmaster of the Falls.
To add another wrinkle of weirdness here, the Mimic-Huntmaster will even trigger the "whenever this creature transforms into Huntmaster of the Fells" trigger each time it transforms. This kind of trigger is a little strange. It doesn't mean that the permanent actually has to change characteristics. Instead, it triggers if the object transforms and it has the specified characteristic immediately after doing so.
Day 'n' Nite
Daybound/nightbound cards are a flavor of transforming DFC found in Innistrad: Midnight Hunt and Innistrad: Crimson Vow. Unlike "regular" transforming DFCs, which usually have a trigger to transform them, these cards are bound by the game's day/night cycle. Hence the name, see.
Day/night is a designation sort of like monarch. It isn't part of the game normally, but once a card introduces it to the game, it lasts forever. If it's day and the previous turn's active player (or active team) didn't cast any spells, it becomes night. If it's night and any of the previous turn's active players cast two or more spells, it becomes day. Some spells and effects like Unnatural Moonrise can also change the day/night cycle.
This day/night song and dance is the only way for a daybound/nightbound card to transform. Sorry, Moonmist fans - these Humans are stuck as Humans until it becomes night somehow.
Players always cast daybound/nightbound spells face up, as their daybound side. If it's currently night, the permanent enters the battlefield with its nightbound face up.
Funnily enough, cards with disturb were also introduced in Innistrad: Midnight Hunt. Disturb lets a player cast a transforming DFC spell from their graveyard for an alternate cost. In doing so, they put the spell on the stack transformed.
So, if I cast Dorothea, Vengeful Victim // Dorothea's Retribution from my graveyard, a few things are true. First, its mana value is 2, as mentioned earlier; it's a legal target for Spell Snare. Other than that, it has all the characteristics of its back face. It's an Enchantment -- Aura, so it's affected by cost reductions like Jukai Naturalist's. Since it's an Aura spell, it also needs a legal target to be cast.
The back faces of disturb cards all have a clause to exile them instead of putting them in the graveyard. Note that this does matter while it's a spell on the stack. If my opponent counters my Dorothea's Retribution, it gets exiled.
This is just a taste of the various and sundry double-faced cards in the game. We've also got modal DFCs and, technically, meld cards. But those are topics for another time.
Question of the week: What's your favorite transforming double-faced card? (Mine is Huntmaster of the Fells)