Boosters

From Spirit of the Dice Wiki

If the booster packs for Spirit of the Dice were real, they would help you make your decks better and stronger, but this game is not big enough yet to make booster packs. This is what they would probably look like if they were real.

Each pack has a different "set".. Obviously, Warriors Remorse has Warrior type cards and cards that support Warriors, and Lords and Devils contains Angel and Demon type cards and cards that support Angels and Demons.