K.24.1- Split cards have two complete card faces on a single card. [CompRules 2001/07/23 - 505.1]
K.24.2- When you play a split card, you announce which side of the card you are playing before taking any other actions as part of the announcement. [Invasion FAQ 2000/10/03]
K.24.3- While on the stack, the spell only counts as the side chosen during announcement. The other side is completely ignored. [CompRules 2001/07/23 - 505.2]
K.24.4- While in all zones other than the stack, the card counts as having both sets of characteristics. It has two names, two mana costs, and so on. [CompRules 2001/07/23 - 505.2]
K.24.5- Split cards are considered multicolored cards (except when they are on the stack). [CompRules 2001/07/23 - 505.3]
K.24.6- If asked to name a card, a split card's full name includes all of its names. For example, if someone names Wax/Wane, it affects the card, but someone naming just Wax or just Wane would not be naming the card. [CompRules 2001/07/23 - 505.7]
K.24.7- Effects that check if a split card's characteristic matches a given value get only one answer but both sets of characteristics are checked. For example, if an effect checked if Wax/Wane was green, it would find this true since one half is green and the other is white. For example, if Void is played on you with a choice of 2, Wax/Wane would not be discarded since neither side has a converted mana cost of {2}. [CompRules 2001/07/23 - 505.6]
K.24.8- Effects that ask for a split card's characteristic in order to use the value (at any time other than on the stack) get both answers. For example, Infernal Genesis asks for the converted mana cost of the card. Wax/Wane would report {1} and {1} since it cannot report a single value. Infernal Genesis uses this as a number, so it adds them together and puts 2 tokens into play. [CompRules 2001/07/23 - 505.5]
K.24.9- Effects that compare a split card in the graveyard, or any zone other than the stack, against a spell on the stack will match the card and spell no matter which half of the spell is being played. For example, Bazaar of Wonders will detect either Wax or Wane being announced when a Wax/Wane is in the graveyard. [DeLaney 2000/10/19]
K.24.Ruling.1- Even though the card has two sets of characteristics on the front, it is still considered only one card for purposes of draw, discard, and similar effects. [CompRules 2001/07/23 - 505.4]