Stats
Stats are bell-curved (3-18), with the range 10 or 11 accounting for "average" members of a species. Stats are used as the base of all checks. In some instances where multiple stats are used for a skill, take the average of those stats and round down to find the stat modifier, known as the stat bonus. The stat bonus is calculated by subtracting 10 from the stat. So, for example, a stat of 12 would give a stat bonus +2, a stat of 10 would give a stat bonus of +0, and a stat of 7 would give a stat bonus of -3.
Stat Bonus = Stat-10
Stat Bonus for FIN would be FINb
Example: FIN(13) so FINb = +3
A useful (albeit clunky) acronym you can use to remember stats is FABSIMN, pronounced "fabsim," just remember to add an "N" at the end.
Finesse (FIN) – agility and dexterity, hand-eye coordination and athleticism.
Allure (ALL) – beauty and charisma, measures influence over others. Perhaps if somewhat ugly but very persuasive, beauty may be treated as ALL-2 while social skills are treated as ALL+2, but ALL skill is still used in most checks (your looks distract from your words, i.e. you have a face made for radio).
Body (BOD) – health, endurance, possible indicator of overall mass.
Strength (STR) – brute force and carrying capacity of character, possible indicator of overall mass (choose STR or BOD to represent mass of character). If carrying another person, compare STR to BOD or STR, with half of difference affecting other actions as a penalty.
Instinct (INS) – five senses and judgment of intentions; a measure of animal intelligence.
Mentality (MEN) – logic, reasoning, and cunning; a measure of sentient intelligence.
Nerve (NER) – self control, discipline, restraint, will power; can be used to ignore pain (CP penalties).
A base stat check would be 3d6 + stat bonus. Skills, gear, and situational modifiers may further adjust this bonus. Skills provide a skill bonus (equal to the skill rank), gear may provide positive or negative bonuses, and finally situational modifiers may further modify the roll. This means a check may be 3d6 + stat bonus + skill bonus + gear bonus + situational modifiers, rolled against the target number (typically 10 for uncontested rolls).
Example: say you have a skill called Blunt that governs the use of your mace, at +2 skill, based off your STR which is 13 (so +3 stat bonus). Let's also assume that the mace is well balanced and imparts a +1 to hit. Your bonus to hit with that weapon would be:
+3 (STR) + 2 (Blunt skill) +1 (mace) = +6
Stat bonuses are also used calculate your physical/mental conditions and tactics. Stat bonuses applied to conditions is always divided by two, rounding down (as always). Remember, with negative bonuses, rounding down increases the penalty (so, for example, a -5 penalty divided by two is -2.5, rounded down to -3). Each condition is calculated by adding a base stat, plus the bonuses of two other stats.
Example: let's suppose you have a character with a BOD of 13 (tough), a INS of 10 (average), and a MEN of 7 (dumb as a sack of bricks). Then her stat bonuses would be:
BODb = +3 INSb = +0 MENb = -3
1/2 BODb = +1 1/2 INSb = +0 1/2 MENb = -2
Physical Condition (PC) – the amount of injuries you can take before collapsing: BOD + 1/2 STRb + 1/2 FINb, minimum 10.
Wounds (W) – the amount of physical damage the character can take: PC - wounds taken. At zero or below, character collapses, gravely injured (NER check needed to remain functional).
Mental Condition (MC) – the amount of mental damage you can take before collapsing: NER + 1/2 INSb + 1/2 MENb, minimum 10.
Stress (S) - the amount of mental damage taken: MC - stress taken. If zero or below, character collapses stunned (NER check needed to remain functional).
Condition Penalty (CP) – This is a penalty to all actions, accrued as the result of taking too much physical (W) or mental (S) damage. If either wounds or stress drop below 10 points, each would accrue a -1 condition penalty (so -2 if both are at 9 or lower). If either drops below 5 points, they accrue an additional -1 condition penalty. For example, if a character had Wounds at 5 and Stress at 4, they'd have a -3 condition penalty. Having both stress and wounds below 5 gives a CP of -4. If either stress or wounds drops at or below zero, add another -2 CP. So, at a maximum, if both stress and wounds are at or below zero, that character suffers a -8 CP.
CP affects all checks. For each action taken, a character may opt to make a NER check, using the results to reduce penalty (or, if failed, take failures as S damage). Successes are essentially working through the pain, while failures means you suffer additional pain from the attempt.
Tactics – 1/2 INSb + 1/2 NERb + 1/2 MENb, this pool may be split or focused for defense (dT) or offense (oT), as long as dT + oT equals tactics. Full tactics is used for initiative (condition penalty applies). Minimum tactics is +0.
Size
While the bell-curve of stats accounts for the average range of a particular type of creature, an average-strength man is no match physically for, say, an averaged-strength elephant, so size category is important to determine such an outcome. Any creature of one size category attempting to affect another of a different size suffers a penalty or gains a bonus in some circumstances.
Here are the basic size categories, listed in ascending order:
S0 (Tiny) - less than 1 kg, from insects to mice, the smallest size category.
S1 (Little) - typically between 1-5 kg, the size of a cat.
S2 (Small) - typically between 5-50 kg, the size of a medium-sized dog or child.
S3 (Normal) - typically between 50 to 200 kg, the size of an adult human or large dog.
S4 (Large) - typically between a 200 to 1,000 kg, examples include cattle, lions, and bears.
S5 (Huge) - typically between 2 to 10 metric tons, examples include elephants and the T. rex.
S6 (Massive) - typically between 10 to 50 metric tons, such as many whales and the Diplodocus.
S7 (Gargantuan) - typically between 50 to 100 metric tons, such as larger baleen whales and the largest dinosaurs.
S8 (Colossal) - 100 to 200 metric tons, the largest creatures to ever live on earth (such as blue whales) would fall into this category.
S9 (Mythical) - beyond 200 metric tons, such a creature could not naturally exist on a world like earth.
For each size category difference, use the following rules:
Weapon sizes against smaller/larger category: raise/lower weapon sizes for each category. For example, when a large creature attacks a normal one with a light weapon, that weapon increases to medium size. A huge creature attacking a normal-sized one with a normal weapon would increase two, one to heavy, one to heavy+1.
Attack rolls against smaller/larger category: -1/+1 per size difference (easier to hit larger targets, harder to hit smaller ones). For example, in a fight between a small creature and a Large one (two categories difference), the Large suffers a -2 to hit the small, while the small gets a +2 to hit the large.
Opposed BOD or STR checks: larger gets +2 per size difference, smaller gets -2 per size difference. So in a contest between a normal creature and a gargantuan one (four categories difference), the normal suffers a -8 while the gargantuan gets a +8... it's unwise to get into a physical contest with a creature much, much bigger than you.
Damage: x2 per size difference against smaller targets, x 1/2 per size difference for larger targets. For example, in a fight between a small creature and a normal one (one category difference), the small creature is only doing 1/2 damage to the normal one, while the normal creature does double damage against the small one.
Example (attack/damage): Say a normal-sized character attacks a huge monster with a sword. As the monster is two size categories bigger than the character, he would get a +2 to hit but damage would be 1/4 normal. Let's say he hits for 9W damage, that's 9/4 (remember to round down) which comes to 2W damage.
Example (opposed stat checks): Say the same character (2 size categories smaller than the monster) tried to physically subdue the threat with an opposed strength check. Let's say his STR=15 (so +5 STR bonus) and the monster STR=13 (+3 STR Bonus). With their size differences, the character's STR bonus suffers a -4 penalty, while the monster enjoys a +4 bonus. This would bring their final bonuses to character +1, monster +7.
Let's say he still rolled better than the creature and wrestled this monster to the ground. On the monster's go, if it wishes to break free, its size really helps, as these bonuses still apply.