I think the Breathers and Breaks rule brings a much needed element to any dungeon-centric game - it allows for longer dungeon crawls without fear of them becoming a slog as the players get whittled down. It also provides an alternative to the infamous "full night's sleep in the middle of a monster-infested dungeon" that can cause pretty big debates at the table. And, as a sucker for battlemages, the Arcane Fatigue rule adds a nice spin and a level of realism to the archetype. Overall, these setting rules will be great for a grittier, more immersive fantasy game while still feeling fair for players and DMs alike. I will definitely be using this for future campaigns.
[5 of 5 Stars!]