Side Deck

The Side Deck is a mechanic present in Act I, Act III, and the Finale sections of the game. When the player draws a card at the start of their turn, they have a choice between their main deck or their side deck. The side deck typically provides lower-cost, albeit less effective, cards compared to the main deck.

Act I

In Act I, the player starts out with a side deck of Squirrels. They are guaranteed to start every combat with one additional squirrel in their hand, totaling ten costless cards available without using items. The squirrels can also be replaced by bees after solving the third painting puzzle.

Act III

In Act III, the side deck consists of Empty Vessels. They later get upgraded to Gem vessels, which provide Mox as well. This side deck is the only one not to contribute directly to the cost system of the segment, namely Energy, although the Empty Vessels can be upgraded to have Battery Bearer.

Finale (Grimora)

In this segment of the Finale, the side deck consists of Skeletons, the only side deck cards who cannot block incoming damage, apart from the optional Kaycee's Mod Aquasquirrels. They cannot defend attacks, because the moment they attack they perish due to their Brittle Sigil. This does, however, mean that they generate Bones, which can then be used to play stronger cards. Skeletons are also the only side deck cards that can innately deal damage, excluding Bees.

Finale (Magnificus)

In this segment of the Finale, the side deck consists of Mox cards, Emerald, Sapphire, and Ruby. These are the only side deck cards that have 3 variants, excluding the Gem Vessels, but those are just upgrades to Empty Vessels.