Sanity

Those who wish to push magic beyond limits may find their sanity strained. A player's maximum sanity point pool is equal to four times their sanity score.
At the end of every long rest, a player who has begun down the path of madness makes a sanity save. A player gains or loses a point of sanity for every two points of difference between the DC and the final outcome of their save. Any bonus that typically apply to saves must be active for the vast majority of the rest in order to apply to this save. The base DC is 5 but will increase over time and may increase based on the trials of the day.
By default, sanity may be spent to add an additional dice to any charisma saves made to resist magic. A player may learn to spend this sanity in new ways as shown in the mini-feats page.
The cost of the die spent is the maximum value on that die.