107.3a
This rule marks the spot where the value of X in a mana cost, alternative cost, additional cost, or activation cost is X-plained. It includes this sentence: "While a spell is on the stack, any X in its mana cost equals the announced value." While true, this sentence was incomplete, in-X-plicably X-cising alternative and additional costs. Those two are no longer X-cluded. X-ellent.


205.3
This rule contains the list of Planeswalker subtypes. We apparently missed a little product called Magic: The Gathering—Commander (2014 Edition). So a belated welcome to the party for Daretti, Freyalise, Nahiri, Nixilis, and Teferi. Narset also joins the list after transcending.


207.2c
Formidable is added to the list of ability words.


613.3e
This rule is layer 7e, where effects that switch a creature's power and toughness are applied. I kept getting questions about what happens if a creature's power and toughness gets switched twice, so I decided just to make it one of the examples.


702.36e
This is a new rule for megamorph, a variant of the morph ability. "Morph" was changed to "a morph ability" in a few other subrules of 702.36.


702.109.
For those of you who enjoy sacrificing things for fun and profit, here's the new exploit rule.


707.1
We made a small editorial tweak to remove the somewhat nonsensical "cards and abilities" to describe what allows spells and permanents to be face down.


713.1c
It wasn't clear what happened if an effect ended the turn during a cleanup step, so a clarification was made. In this unlikely occurrence, a new cleanup step begins. Essentially, you can't escape a turn without going through a "clean" cleanup step.