This is a summary of the rules changes coming to Magic with Strixhaven: School of Mages. If there should be a discrepancy between this summary and the official rules, the official rules take precedence.
New and Updated rules
What used to be called the "converted mana cost" will now be known as the "mana value," and all references to it in the Comprehensive Rules have been updated accordingly. The meaning of the term is still the same and is defined in rule 202.3.
Activate only as a
. . .
Cards that allow you to activate an ability only any time you could cast a sorcery or an instant now say "activate only as a sorcery." Or "instant." But not "sorcery or instant." You know what I mean. Many rules have been updated accordingly.
Magecraft joins the list of ability words.
Sometimes life teaches us lessons. Sometimes those Lessons are cards we've brought into the game. Sometimes the Lesson wasn't good enough and we decide to pick up our cards and go shuffle up for a new game. This rule now clarifies that cards I brought into a multiplayer game leave the game with me when that happens.
These are the rules that handle the phrases "activate only as a sorcery" and "activate only as an instant." 602.5f was added to clarify that cards with the old text have received errata.
Players paying close attention during preview season noticed that Strict Proctor has an odd trigger condition and effect that wouldn't quite work right under current rules. Sometimes, Strict Proctor's ability would end up placed on the stack underneath the ability it was trying to counter. This rule has been changed to make putting triggers on the stack a two-part process, ensuring that Strict Proctor can always enforce its requirement.
This rule says that an effect that refers to a "milled card" can find the card in the zone it moved to. But some cards, like Anowon, the Ruin Thief, don't use exactly those words. We made the reference more generic to cover everything.
This is the rule for the learn keyword ability. It will be on the test.
This is the rule for ward. It forced its way in under the other evergreen keyword abilities and pushed the rest of the keyword abilities down a spot to make room for it. The other rules tried to stop it, but nothing they threw at it seemed to stick. Many cross-references throughout the document were updated.
There's no better way to learn a new rule than to have someone show you how it works. If that's not an option, you can just read this rule that tells you how the demonstrate keyword ability works.
This rule covered what happens in a multiplayer game if a player who has already left the game is required to make a choice. It wasn't clear whether (or how) that applied if the choice they were making was about paying a cost. A new rule in this spot makes it explicit—the cost isn't paid—and the rest of the rules in this section moved down a letter.
Fractal and Inkling
New Glossary Entries
Demonstrate, learn, mana value, ward
Revised Glossary Entries
Converted mana cost is now obsolete. All references to it now use "mana value" instead.
Object now includes "an emblem" in its definition.