From Mtg-News. I don't know how recent this is since I hadn't checked the spoiler for a couple weeks, but this is some general information on the set:
There is a mechanic called "Soulshift" on a handful of CHK cards. It appears only on spirit creatures, and states "Soulshift 2 (When this is put into a graveyard from play, you may return target Spirit card with converted mana cost 2 or less from your graveyard to your hand.)" It isn't known if there will be cards with Soulshift 1, Soulshift 3, etc. There is a subtype of Sorcery and Instant spells called "Arcane". It isn't known if Arcane does anything itself, but we know that some cards trigger a bonus when you cast an Arcane spell. Split cards are back, this time in creature form! You cast them in one form, and when you meet a certain trigger (such as dealing damage to an opponent), you "flip" the card around (basically turn it 180 degrees). On the other half of the card is another creature with a totally different name, abilities and power/toughness. In this way, you get two creatures on one card. WotC has gone back to printing colored mana symbols on cards, which we can all appreciate. They also changed their policy on how to word discard effects. The new wording, which it should have been all along, is "target player discards a card". No more "chooses and discards" or "discards a card from his or her hand". They also changed the wording on legendary cards. Instead of "Creature - Human Legend" we will see "Legendary Creature - Human". Speaking of legends, there are at least 60 in the set. Equipment is now a permanent type of card and there are a few Japanese-style equipments in CHK. Enchant creature cards are back after being almost nonexistant in the Mirrodin block. There are no gold cards in the set. There are 50 cards of each color and 36 left over for artifacts and nonbasic lands. There are at least 5 legendary lands.
I think the most interesting mechanic out of all of these are the "split" creature cards. Should be interesting. An example of this mechanic from the spoiler:
Akki Lavarunner - 3R
Creature - Goblin Warrior
Haste
When Akki Lavarunner deals damage to an opponent, flip it.
[Tok-Tok, Volcano Born
Legendary Creature - Goblin Shaman
Protection from red
If a red source would deal damage to a player, it deals that much damage plus 1 instead.
2/2]
1/1
Illus. Matt Cavotta
153/306
Rare
Thoughts?