Below is an in-depth breakdown of the game's card system, as it currently stands. This is more of a design document than it is a guide; I felt it necessary to make this a public reference, in order for those who see issues with the system to better pinpoint flaws and give more substantial feedback. Attempts at innovation are prone to falling flat - hopefully, through transparency, that can be avoided.

Cards come into play during combat, and are synchronous with the game's resource system. So let's introduce the resource system first.

COMBAT RESOURCES

Determination is the first of Escher's class-resources. Determination is the first of Escher's class-resources. This resource operates similarly to classic TP or SP in usage; it can then be expended to use either Inherent Skills, or Equipment Skills. It's more akin to a deck-building 'currency' though in how it must be generated, much like Treasure in Dominion.

Inherent Skills, as the name implies, are always-available abilities, with a low Determination cost. The idea is an extension of the 'Critical' attack seen in Grandia. Instead of one 'alternative' attack, the player can choose from a set, and grow that set as they progress. Remnant Skills fall under this category too.

Equipment Skills are tied to the gear you bring into combat. A shield, for instance, would grant a Shield Bash skill that stuns enemies. These skills can also be progressed through gear upgrades, which require Familiarity with the appropriate piece of gear. Each use of the Shield Bash skill increases Familiarity with the shield. Once Familiarity is fulfilled, the shield can be upgraded using the appropriate crafting reagents. Along with improved stat modifiers, it would provide another Equipment Skill to be used in combat: Shield Guard, for example. Intuitive, right?

Delirium is a secondary class-resource that operates very differently.

Despite being determined, Escher is at high risk of losing his sanity. Delirium also starts empty, slowly fed by any use of the REMNANTS OF SODIS. This resource can be better understood as something to be managed - once full, Escher is inflicted with the Delirious state, and that's bad news for the party.

Both these resources are conserved between battles.

But where are the cards? 

Silly reader. These resources are the cards.

ON PARTY DYNAMICS

The two resources above, which you'll have noticed are Escher's class resources, are the backbone of card-play, despite the party-wide importance of that card-play. Clarification on party dynamics during combat is thus warranted here.

In the traditional JRPG, the main character and party members exist on what's for the most part a level plane. In a way, the player is the party as a whole. The intention with SODIS is to experiment with a novel approach to party dynamics, where the player embodies Escher during combat to the same degree as they do in the narrative.

Escher leads the party in being the Card Player: his role during combat, and his ability set, is thus catered in great part to the purpose of deck-building, and gameplay during his turn is extended to include our card-play. His companions, Noether and Dirac, are also designed to each have a unique playstyle and role in combat, but with a more secondary influence on the rotating hand of cards. The desire is for controlling each of the three to truly convey the circumstance of three distinct combatants fighting together, as opposed to stat distribution and a few abilities being the exclusive source of distinction in playstyle. Think 'Class Fantasy' in the sandbox Western RPG.

ON OVERCOMPLICATION

A combat system deriving from Grandia's is already as complex as classic JRPG combat comes. Integrating a deckbuilder as part of the core system, without caution, I'd imagine could very easily lead to a bloated, overcomplicated final result, something that could be mechanically sound but more painful than enjoyable to play. See: 'trying to fix what ain't broke'.

My caution comes in the form of a separation of the core aspects of combat, into two distinct but highly-complementary systems.

Generally, resource and state management would be limited to comparing ability costs, or forgoing action on a certain turn to use items or abilities that apply states. By this separation, resource and state management can be fleshed out - gamified separately. The player must now play the deckbuilder in parallel to the more familiar Grandia dance in order to fight effectively, and the parallel arrangement should prevent either system from overcomplicating the other.

Earlier in development, I considered a combat model more in line with games like Slay the Spire, where the entirety of combat is within the card game. I felt that, in that model, the scene of the battle was simply a visual representation of the card play, if that makes sense. But I often envision SODIS as a tabletop RPG, and I felt that battles should feel more like a board game where you play cards onto the board, as opposed to a purely card-based game. I feel that the current iteration serves to achieve the desired feel of gameplay much better.

With that out of the way, let's get started.

THE STARTING DECK

Escher begins his journey with a Starting Deck of sixteen cards. At the start of any battle, this deck is shuffled and forms the Draw Deck. At the start of each of Escher's turns, four cards are drawn from this deck to the player's hand, and two must be played, as in, used then discarded. The remaining two cards are then discarded without being used. 

Thus, a card may have two types of effect: 

On {Played}: ----

On {Discarded}: ----

Escher can then proceed with his turn in traditional JRPG combat, and the cycle repeats.

Using Skills can Manifest a specific card. Any card manifested goes directly to the discard pile. Using Shield Bash, for example, manifests the Walking Bulwark card. Upgrade the shield through crafting, and Walking Bulwark becomes part of your Starting Deck.

Once the Draw Deck is depleted, the discard pile is reshuffled to form a new Draw Deck.

CARD TYPES

EMPTY

The Starting Deck contains six of these obscure little things. 

The Purge action would be the equivalent of tearing up the card: it's removed from play, for the duration of battle.

Useless?

SOURCE Cards

These cards grant Determination once played, and thus are the crux of your deck. They can also have secondary effects: allowing an extra card to be played that turn, for example.

STATE Cards

These cards are used to apply States to yourself or your allies. By choosing not to do so on a certain draw, and letting the thought cook, the State card Grows: Recklessness would become Recklessness (2), with each of the stat-changes shown doubled. After a second growth to (3), the State is Purged upon being discarded, adding the nuance to state management of the player having to time the application of states.

STRESS Cards

Each of these cards holds a pair of detrimental effects, designed to mess up your shit.

The {Discarded} effect is usually of greater detriment than the {Played} effect.

The Stress card shown is the only example from the Starting Deck: one of sixteen. But you may find certain enemies to be good samaritans, eager to help you by Injecting cards of a certain type into your deck.

And thus, your Empties can be a buffer against drawing Stress cards, if you choose to conserve them.

SUPPORT Cards

These cards are manifested to your deck by your allies, when they use Skills.

THE REMNANTS DECK

The following is a a system planned for the mid-to-late game, that hasn't been implemented yet as of the Public Build. I felt that the core system should be iterated upon and refined further before the Remnants and Delirium system is tied in.

Using a Remnant Skill with an equipped remnant brings into play the Remnants Deck, an alternative Draw Deck placed on the opposite side of the table, and draws from it a card. We can call this 'activation'.

This card, just like one manifested, goes directly to the discard pile... except face down.

.

Each Remnant gives access to a pseudo skill tree that forms part of buildcrafting. Advancing each tree allows you to obtain more Remnant Cards, and grow the deck you have assigned to each Remnant.

These cards are distinct in that they are also assigned a value.

These values pertain to an increase in Delirium, when {Discarded}. {Played} doubles that increase.

Excepted from this are three Dump values, that decrease Delirium by 10, 15, and 20 respectively. These would be rare in your deck, and assigned to cards with especially significant effects.

If you're wondering about the suits shown, each happens to pertain to a Remnant. We'll be blasphemously appending two new suits accordingly. A synergy between cards in-hand, based on suit and value, is to be implemented.

All this is not much more than a loose framework for the moment. Ideally, it should be intuitive enough to be picked up smoothly by the player, and balanced enough to push a stream of tough decisions automatically.

More to come.