From VPG:
Seasons are 50-card packs that expand upon the current Age (in this case, Age of Revelations). Each pack includes at least one new Deity card plus new cards for each faction (and a few original base game cards) with enough copies to reach your full deck-building potential.
A copy of Twilight of the Gods: Age of Revelation is required to play.
In Season of Prophecy, the forces of Sanctuary emerge from behind their walls to take the fight to their enemies. Led by the Norse goddess Freya, these new cards accelerate Sanctuary’s early game options and allow for a more proactive and aggressive play style. 
In Season of Epiphany, the adherents of Mysticism tap deeply into primal sources, bringing a bevy of new destructive effects to bear on all who would oppose them. Bolstered by such powerful cards as Aether Implosion, and the emergence of Yggdrasil, the World Tree, Mysticism followers gather behind Horus to dominate the battlefield. It remains to be seen if the new powers gathered by the other factions can withstand the oncoming storm…
Aggression and Negotiation’s rivalry bursts into open conflict with the introduction of Indraand Hermes in Season of Apocalypse. Backed by potent new epic creatures, including Alexander the Great and Melanippe, the Black Mare, the roiling conflict between pantheons threatens to encompass the entire globe and lay waste to all that exists. Will this be the final battle of the gods? Only time will tell…
