The set's theme is color, utilizing hybrid (as seen in Ravnica) across the allied color pairs, along with new innovations in hybrid mana. A new keyword action is introduced in this set, called "Q", in place of the untap symbol; according to Rosewater, this has been "never done before.". Rosewater also stated that "the set plays into the duality theme between Lorwyn and Shadowmoor blocks, both in the art and the mechanics", for instance the same creature types will return. Moreover Rosewater claimed that the set will play on the same plane as Lorwyn, but due to an event called the Aurora, the plane and its inhabitants were twisted and changed. The previewed art of Shadowmoor's booster packs confirms this concept, depicting familiar Lorwyn creatures either during or after a dark change. The set has a strong hybrid mana theme, revealed in a sample booster on magicthegathering.com.

Five theme decks will be released as part of the set. The preconstructed theme decks are: "Aura Mastery" (White/Blue), "Mortal Coil" (Blue/Black), "Army of Entropy" (Black/Red), "Overkill" (Red/Green), and "Turnabout" (White/Green).[7]

Mechanics
The following are mechanics released in this set:

Persist - When a creature with persist is put into a graveyard from play, if it had no -1/-1 counters on it, return to play under its owner's control with a -1/-1 counter on it.

Untap - The untap keyword action now has a symbolic representation.[8]

Themes
The following are themes found in this set:

Hybrid Mana - Cards have mana costs which may be paid by either of the two colors listed. This results in cards that can be multiple colors, but paid for by a single color source. It also results in cards like 'Rhys, the Redeemed' who cost one hybrid mana, but count as multiple colors.