With regards to shadow dice, I think you have mechanics that encourage the use of the dice. Allowing players to use unspent dice for experience means almost all of them will save rather than use them. I suggest either (a) dice cannot be saved for experience or (b) you get the experience bonus for dice earned, not dice saved. Personally, I'd suggest (b). Also, I'd suggest the dice must be used by the end of the session.

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