Two types of rolls:
Opposed Rolls
Each side rolls 2d6 + Modifiers. d6’s explode on a 5 or 6 (roll another d6, which can also explode). Margin of success = difference between rolls.
Simple Rolls
3d6 + Modifiers. d6’s explode on a 5 or 6 (roll another d6, which can also explode). Margin of success = total – DC.
Mathematics
The system generates unbounded bell-like curves. This allows unbounded bonuses and skill levels. Net modifiers shift the bell curve – this gives diminishing returns to hyper-specialization against fixed opponents while still making every bonus count against equally specialized opponents.
Roughly speaking, a +5 bonus doubles your chance of success / cuts your chance of failure in half (depending on which side of the bell curve you are on). This allows us to create tiers of play for every skill:
+0: Untrained
+5: Skilled
+10: Expert
+15: Master
+20: Grandmaster
+25: Legendary
Near the balance point (50/50 chance of success), a +1 bonus equates to about a +5% chance of success. The relative value decreases with each tier of separation:
1 tier: 3.5%
2 tiers: 2%
3 tiers: 1%
4 tiers: 0.4%
5 tiers: 0.2%
Margin of Success & Damage
Damage on an attack = weapon base damage + margin of success, then reduced by armor.
Typically attack bonuses are around 5 points higher than defense bonuses. The following are typical margins of success for each tier of skill difference in favor of the attacker (first number is expected, second number is 5% critical):
-3 tiers: 6.6 / 5
-2 tiers: 7 / 10
-1 tiers: 7.7 / 15
0 tiers: 9.5 / 20
1 tier: 12.5 / 25
2 tiers: 16.5 / 30
3 tiers: 20.5 / 35
Calculating Damage
On a hit, first subtract the attack’s armor penetration from the defender’s armor to determine their effective armor for the attack (note: large and powerful creatures have high armor penetration, such that heavy armor becomes less effective against giants, dragons, and other large monsters).
The attack’s base damage = base weapon damage + margin. If the effective armor is higher than the base damage, the attack deals only stamina damage, not physical damage.
Finally, reduce the base damage by the defender’s Soak rating (a function of armor, body, and general toughness), to a minimum of half the base damage. All characters have the same number of hit points, so the Soak rating describes the general difference in toughness between characters.
Situational Advantages
Situational bonuses grant the player additional dice to roll. The general idea is that a character has a base score written down on their character sheet that rarely changes. Anything that modifies their bonus for an encounter or shorter grants them additional dice to roll, underscoring that these are temporary and reducing the number of modifiers the player has to hold in their head. Bonuses come in three flavors, and are added to the results of the roll:
- Minor: (special d6 with 0, 1, and 2 faces). These don’t explode (expected value: +1)
- Moderate: 1d4. These don’t explode (expected value: +2.5)
- Major: 1d6. These explode (expected value: +5.2)
Bonuses larger than major add multiple d6’s.