Backstabs allow thieves to do a large amount of damage with a single blow
from a stabbing weapon.  As stealth is required, a rogue cannot do this
while already in combat.

   Well-aimed and particularly powerful backstabs may damage the spinal cord
of the victim, crippling them.

   Potential victims stand a good chance of avoiding such attacks by keeping
an eye on the sneaky little bastards with the `watch' command.  Stabbing an
NPC will cause them to automatically watch you.

   Damage: 
      Weapon damage * backstab_multiplier / 8

      Backstab Multiplier:
         20 + level

         Target Asleep?
            +20
         Target in Combat?
            range(multiplier / 4, multiplier - multiplier / 4)
         Target doesn't have a spine?
            /3 
         Wearing back armor?
            - armor value * range(3, 6)

   Cripple Effect:
      Opponent must make a fortitude save or become crippled. They receive
      a bonus to their fortitude save based on the power of the backstab.
      Baseline, it is a +30 modifier, making it almost impossible to cripple
      them.
      
      Damage > 160: -6
      Damage > 120: 0
      Damage > 80:  6

   Armor Modifier:
      Damage > 160: -20
      Damage > 120: -15
      Damage > 80:  -10
      Damage > 20:  - 5
      Missed Stab:  +10


   Example:
      Level 10 - 2d9+6 - Awake - No Combat - No Back armor
         Weapon Damage Roll: 2d9 (10) + 6 = 16 
         Multiplier:
            20 + 10 = 30
         Damage: 16 * 30 / 8 = 60
         Fort Save: +30
         Armor Mod: -5

See Also: Rogue, Combat, Protect, Watch