I know ther are some rules for creating custom Investigators, so new character is balanced and does not ruin the game. It's utilized in Strange Eons.
Are there any rules for custom special abilities for Investigators?
I am creating custom Investigator, who is psychologist like Carolyn Fern, but I don't like to copy her ability. Instead, I thought about ability to restore Sanity in exchange for Clue tokens in 1-to-1 basis during upkeep. Player would be able to use as much Clue tokens as he/she likes and restore Sanity to himself/herself or players in the same area.
I would like to know if there are any rules to check if given special is not over/underpowered.