AEG Announces New Mystic Vale Expansion

Mystic Vale lets players actually customize their cards as they play. Using the clear sleeves, players will insert clear upgrades to their cards, building their deck in an entirely new way. The game already has several expansions, but more is on the way. In this case, it’s Conclave, and it will be available in April.
Plus, the box will be able to hold all your current sets.

From the post:

The Ultimate Mystic Vale Storage System, Expands Game to 6 Players & Adds More Expansion Content

As the struggle to restore the Valley of Life intensifies, the ranks of those combating the curse continues to swell. Druidic clans from across the land heed the call, including the Frostcaster and Nightvale clan.