| Required class | Vampire or Werewolf |
| Power sphere | Auxiliary |
| Required powers | Wolf Form 5+, Self Control 10+ or Extended Rage 10+ |
This power toughens your pelt while in Wolf Form or wolfman form, making it as resilient as armour. Each rank in this power gives you +5% armour vs crush damage, +4% armour vs cut damage, +3% armour vs stab damage, +2% armour vs cold and shock damage, and +1% armour vs heat and poison damage. In addition, you gain 1 point of auto-absorb vs crush, cut and stab damage per rank, and 1 point every second rank against other types of damage (see ‘help armour’).
Furthermore, each rank grants you 1% natural immunity to all forms of damage, up to a maximum of 20% immunity at rank 20. The physical damage part of this immunity also applies in human form, giving a max of +20% immunity at rank 20.
Note that if you have Sure Footed or Evasion, their bonuses will be added to your immunity, so both talents plus 20 ranks in Lupine Fortitude would give you 75% immunity to physical damage in Wolf Form (as well as 20 auto-absorb and 100%/80%/60% crush/cut/stab armour, although the latter could be bypassed).