Fortitude
Defensive Skill
Your spend 
Skill Points to increase the chance you resist 
Body altering 
Contesting Rolls.
This can also represent physical training, and related to endurance.
Passive Abilities:-
Healthy Body3000 gp
-
Restful Body5000 gp
Quick Abilities:-
Immortal Tenacity
Free Abilities:-
Unbreaking Momentum
d100
Mod
ADV/DIS