You're one of the Blades, pushed into exile. The cards are based on creatures, characters and lore found in The Elder Scrolls series. In "Abyss", you must fight your way through enemies in both "hand-crafted" and procedurally-generated maps to collect treasure. Part of those measures will likely be a file integrity check, which means that if you modify the game files, you either won't be able to play or worse, you'll be banned.
This final mode will be where players will find a hub of stories and quests which follow their story as a member of the Blades, the top agents of the Empire.