Taking a page from Tibs, I took their proposed rules for 9 and ten players and expanded them a bit. Thoughts?
9 investigators
• Newly opened gates spawn 3 monsters instead of 1 (1-4 invests) or 2 (5-8 invests).
• The monster limit is 12.
• The outskirts limit is -1 (that is, for each monster placed into the outskirts, raise the terror level by 2!). This happens once per turn.
• The number of open gates that immediately awakens the Ancient One is 4.
10 investigators
• Newly opened gates spawn 3 monsters instead of 1.
• The monster limit is 13.
• The outskirts limit is -2 (that is, for each monster placed into the outskirts, raise the terror level by 3!). This happens once per turn.
• The number of open gates that immediately awakens the Ancient One is 4.
11 investigators
• Newly opened gates spawn 3 monsters instead of 1
• The monster limit is 14
• The outskirt limit is -2 (see above). Also, on any turn that at least one monster went into the outskirts, add one to the Doom Track. Strongly Advised to use Burgeoning Gates Rule.
• The number of open gates that immediately awakens the Ancient One is 4.
12 investigators
• Newly opened gates spawn 3 monsters instead of 1
• The monster limit is 15
• The outskirt limit is -2. Also, if monsters go onto the outskirts during the Mythos phase, immediately draw and use an additional Mythos phase. Strongly Advised to use Burgeoning Gates Rule.
• The number of open gates that immediately awakens the Ancient One is 4.
13+
• All rules from the 12 investigators list stay.
• Add +1 monster to the limit for each additional player.
• For every player AFTER the 12th, it takes one additional Clue Token to seal gates. Strongly Advised to use Archives rule to make closing a gate a larger, collective effort.
Optional Rule: Burgeoning Gates
If the number of monsters a monster surge would generate would go over the limit, stop placing monsters at exactly the limit.
If there is a monster surge while the board is currently at its monster limit, the appropriate “Outskirt Punishment” listed above happens.
This rule is intended to make Monster Surges sting, but to take the edge off of the especially unforgiving 9+ rules.
Optional Rule: Archives
Players ending their Movement Phase on a space in Arkham may drop any number of clue tokens on that space, representing them leaving their notes, scrawling, messages, and other recordings for others. Once dropped, these clue tokens are treated as normal.
This is to aid the problem of running out of clue tokens too quickly without tossing out clue tokens like candy. Also, team work!