Devil's Stamina( Fiendish Codex II: Tyrants of the Nine Hells, p. 83)
Your body is infused with the toughness and fortitude of a devil. You can shrug off attacks that would slay a lesser creature.
Devil's Favor (FC2) , base Fortitude save +3,
You gain 2 extra hit points per devil-touched feat you have selected, including this one. These hit points add to your maximum hit points, just like hit points from any other source. In addition, once per day you gain fast healing equal to the number of devil-touched feats you possess for 5 rounds.