The Player Rolled Defenses variant requires the following: 1. * The "10+" for AC, Fortitude, Reflex, and Will defenses for player characters is now a d20 roll ( i.e. subtract 10 from all the PC's defenses and add a d20 roll ) 2. * The DM will add the "10+" to the attack bonus of monsters to set a "target number" for the Player Rolled Defense ... this means the DM will not make an attack roll. 3. * A roll of a "natural 20" is a "Perfect Defense" and allows the defender to make a basic attack ( ranged or melee ) as an immediate reaction. 4. * A roll of a "natural 1" is a "Fumbled Defense" and the attacker scores a critical hit.