Not to overly criticize, but I have a bit of a problem with the Humbled Spirit ability: the duration of immunity for those who make their saves. 1d6 minutes? Seems kind of cumbersome. Does the DM roll for each player and hide the result? Most such abilities allow 24 hours of immunity, which saves player hassle (if they are forced to count rounds until they are vulnerable to a monster's special attack) and DM hassle (honestly, I would likely forget who's invulnerable at given times).

Also, the ability itself doesn't have a duration.