This is a dilution fix that involves controlling the number of each type of mythos card that goes into the mythos deck before the game starts. There are four types of mythos cards that are prone to dilution:
• Cards that refer to the Dunwich board (25 total)
• Cards that refer to the Innsmouth board (35 total)
• Next Act Begins cards (6 total)
• Cards that refer to Exhibit items (9 total)
Keep those four decks separate from the other mythos cards. Then, before the game begins, follow these steps:
1. Choose which of expansions you want to play with (you can choose any or all of them)
2. Based on the expansions you chose, draw some mythos cards at random from each mythos deck, without looking at them
3. Shuffle those cards together to create the Mythos deck that you will use for the game.
You’ll need to spend an extra five minutes during setup to create the mythos deck. But once the game begins, there is no interruptions to the flow of the game. You just turn over a mythos card. Some mythos cards won’t be in the game, but that’s not a problem since you don’t know which cards are in the game and which aren’t. If you draw The Story Continues, just shuffle the discards back into the deck that you made. This method is actually more true to the spirit of The Story Continues, since you have a better chance of re-drawing mythos cards than if you used one huge mythos deck.
The hard part of this method is knowing how many cards of each deck to include. I crunched the numbers for each possible combination of “dilutable” cards. I'll post the numbers below in a minute.
One of the great things about this method is that you are able to stay very close to the “correct” percentage of mythos cards. For example, if you’re playing with just KIY, 6.38% of the mythos cards should be Next Act Begins (6 cards out of 94). With this method, you can stay true to the original percentages while playing with multiple expansions.
If you play just with Dunwich, then 24.27% of the mythos cards should open gates in Dunwich (25 cards out of 103). If you play just with Innsmouth, 33.98% of the card should refer to the Innsmouth board (35 cards out of 103). With just KIY, like I said the percentage is 6.38% (6 of 94).
With just CotDP, the percentage is 10.59% (9 cards out of 85). Also, each of the cards in Curse that refers to Exhibit Items also opens a gate in Arkham. The cards are: Corpses Preserved, Cursed Relics, Escape from Arkham Asylum!, Museum Artifacts Stolen, Museum Haunted, River Breaches the Levees, A Sandstorm!?, and Strange Ornithological Sightings.
Depending on the expansion that you use, the percentage of “other” mythos cards ranges from 66.02% to 100%. When playing with multiple expansions, the trick is to reduce each of these percentages proportionally. As you include more towns, each town will see less activity. That can’t be avoided. However, it’s possible for each town to get the right number of mythos cards relative to the other towns.
I have chosen to never reduce KIY’s percentage. 6.38% is low enough. Also, the chance of drawing an “Exhibit Item” mythos card never has to be reduced because those cards count towards the cards that open gates in Arkham.