Over the years, Ascension games have been released in alternating large and small versions (for up to four or up to two players, respectively), which each game being playable on its own or serving as an expansion for whatever you already owned.
Ascension: Realms Unraveled, due out June 2014, is the fourth large box Ascension game. While cards in previous Ascension games have always belonged to one of four factions, Realms Unraveled introduces multi-faction heroes, and these heroes combine with the new "Multi-Unite" game mechanism to deliver huge rewards to those who play multiple heroes from the same faction. (You can see an example of "Unite" on the Ascension: Michelle, Star Oracle promotional card released in December 2013 to honor Ascension tournament winner Michelle Swan. I presume that Multi-Unite offers increased bonuses when you match multiple factions, but Stone Blade Entertainment — which is what Gary Games changed its name to in Dec. 2012 — has released only one Realms Unraveled card to date.)
Ascension: Realms Unraveled also features the "Transform" mechanism that debuted Ascension: Darkness Unleashed, with players being able to convert their cards into new, more powerful versions as the game progresses.