Comprehensive Rulebook Changes
What are the Comprehensive Rules?
Magic is complicated. No, really. When you have more than 13,000 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.
Ashiok and Xenagos join the list of Planeswalker types.
God, Nymph, and Sable join the list of creature types.
Heroic joins the list of ability words.
301.5e & 303.4j
This rule affects some corner cases with Bludgeon Brawl and Dominating Licid. It's a bit of a deep dive. Still here? Okay then. So, it's possible to have a permanent with an ability that refers to the "equipped creature" that's not an Equipment. Or, you can have one that has an ability that refers to the "enchanted [something]" without being an Aura. In some weird cases, such a permanent can be attached to another permanent.
For example, there was a weird combo with Myr Welder exiling Demonspine Whip and Transmogrifying Licid. The Welder could now become an Aura and attach to a creature. But if it wasn't an Equipment, what did the Demonspine Whip ability mean? Was there an "equipped creature?" At the time, we decided no. "Equipped creature" had no meaning if not on an Equipment. "Enchanted creature" had no meaning if not on an Aura.
This stance was logical, but it had a few unintended consequences. The most glaring was Dominating Licid. It becomes an Aura with "You control enchanted creature." This control-changing effect applies in layer 2. But at this point, the Licid isn't an Aura yet. That doesn't happen until layer 4. By rule, the ability didn't do anything, because it said "enchanted creature" and wasn't on an Aura. Clearly, this wasn't what we had in mind.
So, we're reversing course. Under this new paradigm, laid out in rule 301.5e and 303.4j, "enchanted," "equipped," and "fortified" are really just different ways to say "attached." It doesn't matter what type or subtype the permanent with the appropriate ability is, and that ability will refer to whatever the permanent is attached to.
This rule was created to handle the unusual case of an effect trying to put a permanent that isn't an Aura, Equipment, or Fortification onto the battlefield attached to an object or player. It was written a little too narrowly and didn't handle all the cases it needed to. As an example of how this could happen, say you have an Aura with bestow and Flickerform attached to the same creature. If you activate Flickerform's ability, the card with bestow will return to the battlefield as an unattached enchantment creature.
This rule, covering effects that change land types, got a small tweak. If an effect sets a land's subtype to one or more of the basic land types, it loses all abilities it had. The rule inadvertently left out abilities it may have had due to copy effects, so that hole was closed.
This is a new rule defining the term devotion to [color].
New rules for the keyword ability monstrosity.
New rules for the keyword bestow.
A small typo was fixed.
New entries for bestow, devotion, monstrosity, monstrous, and paired (which I missed at the time).