The Kingdom Deck
I thought of the central deck mechanic as a way to avoid going to down the much-travelled route of summon mons and smash 'em into each other.
Time to brainstorm how that mechanic might work.
In abstract terms the kingdom deck represents a battlefield (in this case the organisations and individuals available to the players to corrupt) and making it a deck of cards is a simple way of varying how each game will play out.
At any time a certain number of kingdom cards will be in play. This can be thought of as a window of access. These are characters that are accessible to the warlock's sexy minions. This window of access will be constantly moving - cards will cycle out at end of turn and new cards come in (representing opportunities to get at an individual passing). Thematically and mechanically this seems plausible. If the current configuration locks all players out from doing anything the game should have a way of keeping things flowing. Effectively the cards in play are a queue. At the end of turn the bottom card is removed from play, all the others slide down and new card is turned over from the kingdom deck and added to the top of the queue.
With that mechanic in place the questions become:
How big should the kingdom deck be?
Big enough to provide enough variety without being unnecessarily unwieldy. Less than 100 and greater than 50 at a rough estimate.
How many cards in play at any one time?
This is the size of the window of access. Too many and it becomes overwhelming. Too few and reduces the possibilities of interaction between kingdom cards. I'm thinking of starting with 12 and seeing where it goes from there.
Is the layout important?
This shouldn't matter. Designate where the top is and where the bottom is. As the game progresses cards cycle off the bottom and new cards are added to the top. It shouldn't matter if this is a line or a grid. The reason we might want to specify a specific layout is it allows for a spatial mechanic. eg. Bodyguard - while this is in play cards adjacent to it may not be seduced and corrupted.
How fast does the kingdom deck cycle?
Do we expect to go through it once or multiple times in a game? This will affect strategy. Deckbuilding games such as Dominion have the player cycle through their own deck many times in a game and having some control over the content of that deck is a major part of the strategy. I'm not sure how it would work in a physical game (as opposed to computer game), but an interesting idea would be a "capture'n'subvert" type mechanic - seduced minions are shuffled back into the kingdom deck. The game would then become about both players try to "build" the kingdom deck (by corrupting some pieces to their side, removing others that are detrimental to their strategy). I think that could be interesting, but probably online only as tagging the characters once they go back into the deck to indicate who had turned them would by tricky to implement in a physical card game.
Then to think about what goes in the kingdom deck. Characters for succubi to target, tempt, seduce and then corrupt to the player's side is the most obvious. So what type of characters?
Basic characters that don't fight and don't have influence. They exist as an energy source for monster girls to slurp energy out of (and give us lots of lovely perversion potential). Also, if we don't mind wandering into grimdark territory, bloody sacrifices required to bring the more powerful demons into play.
Seducing these opens up access to higher tier characters.
While these characters are in play, players are prevented from certain actions (eg a priest that prevents succubi seductions from taking place while they're on the table).
Keys and Blocks are functionally doing the same thing - controlling access to higher rank cards. Main mechanical difference is that a key can be grabbed at any time and used later on the higher target while the block needs to be in play at the same time the target is. If the goal of the game is to capture top-rank "King" cards, it's going to be important that there are Blocks in play while the King is in play.
These cards exist to be a nuisance to the player through things like banishing succubi, rescuing seduced characters, hampering certain magic. Think of them as like random events being turned over for the turn.
Thinking about heroes as mechanical representations also makes me think about when events trigger.
Here are some possibilities:
When the card comes into play (is turned over from kingdom deck at start of turn)
When the card leaves cycles out of play (less important)
And also on player actions:
When a succubus is summoned
When a spell is cast.
We can also have triggers that are specific to spells and succubi of different factions (Most card games divide into groups - e.g. the five colours of Magic: the Gathering).
When a character is seduced
This should give a lot of design space for making cards. (and we haven't even started on the succubi yet!)
Not in-game dangers, but design dangers. I think the game wants the various kingdom cards to be able to interact with each other and the player. The danger there is that if the interactions are too specific (eg limited to one of maybe five factions within the kingdom deck) or there are too many card types, there's a danger there will be too many instances where none of the kingdom cards in play at any one time do anything.
For this reason I like the idea of making the kingdom deck all characters. That way there's more overlap between the types.
e.g. Strategically a player will want to remove Blocks to open up access to other characters. The choices there can be:
a) Very easy - temporarily take them out of the picture. e.g. an arachne sticking them in a web, sending them to sleep with alraune perfume.
b) Easy - removing them permanently. e.g. Nom-noms for the more vore-y monster girls.
c) Hard - seducing them into resource. e.g. Succubus drains them for mana a player can use for spells.
d) Very hard - seducing them and using them as a double agent.
Hmm. I should start thinking about those sexy succubi cards now...