Comprehensive Rulebook Changes
What are the Comprehensive Rules?
Magic is complicated. No, really. When you have more than 12,000 interchangeable game pieces, you get some freaky interactions. The Comprehensive Rules cover everything the game has ever come up with, from basic game play structure, to every keyword ever, to entire pages dedicated to single bizarre cards (hello, Karn Liberated!). The Comprehensive Rules are, well, comprehensive… but they're also obtuse, unfriendly, and looooong. They're not intended to be a player resource—they're a judge resource, a rules guru resource, and a place to store definitive answers. In fact, I honestly recommend never reading them. For a much friendlier rulebook that is intended to be a player resource, check out the Rules Page and download the Basic Rulebook (2.1 MB PDF). It doesn't have sections about phasing or subgames… but you'll never miss them.
This rule covers the case where replacement and prevention effects result in multiple card draws. It makes the timing of handling such cases clear, putting the card draws after any parts of the original event that aren't replaced. However, this should really apply to effects that result in a single card draw also, so this rule is being tweaked accordingly.
Fixed a typo in the first sentence. "Opponent's" becomes "opponents."
This rule covers enters-the-battlefield replacement effects that also move other objects to new zones, such as the ones created by Sutured Ghoul's ability or devour. There are now two subrules, the first saying you can't have the object entering the battlefield go to another zone when applying such a replacement effect (aka Sutured Ghoul can't exile itself when entering the battlefield from a graveyard). The second says that you can only choose to move an object to a new zone once when applying such effects (aka You can't sacrifice the same creature to multiple devour abilities if your Planechase game is on Jund).
This rule covers damage that can't be prevented and how damage prevention shields still are applied to such damage, even though those shields won't actually prevent damage. Now, rule 615.7 makes it clear that a damage prevention shield is reduced by actually preventing damage, not just by the act of applying that shield. So, I'm adding a clarification to rule 615.11 that says your existing damage prevention shields will be intact even after you're dealt damage by Malignus, for example.
Fixed a typo. "Replacements effects" becomes "replacement effects."
Fixed a typo. "The plane card or that's turned face up" becomes "the plane card that's turned face up."
Fixed the same typo that appeared in rule 507.1.
This rule deals with the casting of split cards. I added a sentence saying that only the half you intend to cast is evaluated to see if it can be cast. This matters if one half can't be cast (due to Iona, Shield of Emeria, for example) but the other can. Although it's clear that only one half is considered to be put on the stack, it wasn't clear what characteristics you looked at in the first place to determine whether you could cast either half at all.