This is a summary of the rules changes coming to Magic with the release of Innistrad: Midnight Hunt. The most recently published rules can be found on our rules page. If there should be a discrepancy between this summary and the official rules, the official rules take precedence.
New and Updated rules
New Keyword abilities
This very spooky rule is the one that explains how disturb works and tells us that a card cast transformed also enters the battlefield transformed.
This is the new rule, along with its several subrules, that handles the daybound and nightbound keyword abilities.
This very short rule describes the decayed keyword ability.
Day and Night Designations
502.2 and 502.2a
A new rule that explains the turn-based action that causes the game to become day or night. A new subrule explains how this works in formats with shared turns, like Two-Headed Giant.
This new rule and its subrules cover the day and night designations that the game can have, what language is used on cards to refer to them, and how it changes between them.
General Double-Faced Card rules changes
This rule explains that the mana value of the back face of a transforming double-faced card is based on the mana cost of its front face. Prior to this update, it referenced only permanents. Now, thanks to the disturb mechanic, it also includes spells.
This new double-faced card subrule explains the characteristics of a spell with its back face up and what happens if you copy a spell with its back face up. These both mirror the behaviors of double-faced cards that are back face up on the battlefield.
712.7 and 712.7b
This rule used to say that a transforming double-faced card that is cast as a spell is put onto the stack with its front face up. With the introduction of the disturb mechanic, however, this isn't always true. This rule now also allows spells to be cast transformed and thus have their back face up on the stack. A new subrule explains how that interacts with a spellcasting permission granted by an ability (such as disturb) on the front face of that spell.
This rule used to say that resolving transforming double-faced cards enter the battlefield face up, but much like with 712.7 above, this is no longer always true. The rule now accounts for both disturb and cards with nightbound entering the battlefield at night.
This ability explains how to apply replacement effects that occur "As [this permanent] transforms." Such abilities are applied while that permanent is transforming, not afterward. So, for example, when Leeching Lurker transforms into Curse of Leeches, you choose a player for it to enchant while transforming it. There is no moment of time after it transforms where it is Curse of Leeches and not attached to a player.
Miscellaneous Rules Maintenance and Updates
This rule was updated with Dungeons & Dragons: Adventures in the Forgotten Realms to change the order in which costs with unknown outcomes are paid. In a small number of situations, the wording about hidden zones was a little too broad, so now that part has been dialed back a bit and refers only to random elements or moving objects from the library to a public zone.
The adversary cycle of cards in Innistrad: Midnight Hunt have a triggered ability that allows a player to pay a cost and a second reflexive triggered ability that happens if that cost was paid one or more times. The rule for reflexive triggered abilities is getting an update to make sure this ability triggers only once if the cost was paid more than one time.
Sigarda's Splendor has a linked ability that requires you to note some information and then take an action based on the information that was noted. Those abilities are linked, and this new rule makes that explicit.
How Altar of the Pantheon functions was not well defined for some interactions. This new subrule for devotion makes it clear how an effect that modifies an object's characteristics based on a player's devotion can always see the increased devotion from Altar of the Pantheon.
When the bestow mechanic was first introduced in Theros, copying permanent spells wasn't really something that was being considered for the purpose of the game rules. Recently, however, we've begun to see Magic cards that do copy permanent spells, and the interaction between those cards and bestow was unclear. We're adding this new subrule to make it clear that a copy of a bestowed Aura spell is also a bestowed Aura spell. Its target won't change unless something allows a player to change its target.
There are no new subtypes in Innistrad: Midnight Hunt.
New Glossary Entries
Day, daybound, decayed, disturb, night, nightbound