ATTACK MATRIX

USING THE ATTACK MATRIX TABLES

Find the level (or, in the case of monsters, hit dice) of the attacker on the appropriate chart and matrix that with the armor class of the defender. (See also Character Classes.) 

The resulting number or greater must be rolled on a d20 for a successful hit. Penalties and bonuses may modify either the die roll or the number needed to hit (i.e. the armor class value of the target).

Armor class below 10 is not possible except through cursed items. Armor class above 2 is easily possible due to magical bonuses and dexterity bonuses. To determine a "to hit" number not on the charts, project upwards by 1's (5% increments), repeating 20 six times before continuing with 21.

Monsters with HD+. When using [the Attack Matrix table], any plus in a Hit Die rating above +3 equals another hit die to a maximum of +1 to hit dice. (E.g. 6 + 6 equals 7 hit dice.)

Demi-humans and 0-level NPCs. Elves and half-elves  with no character class use the Fighter attack matrix, while non-player character half-orcs with no character class use the attack matrix for Monsters. Dwarves, elves, and gnomes are never lower than 1st level (unlike halflings, half-elves, or humans, which may be of 0-level) and all use the Fighter attack matrix.

Normal men such as men-at-arms are always considered to be 0-level. (See Non-Player Characters, Hirelings, Mercenary Soldier.)

REPEATING 20 VALUES - PROGRESSION ON THE COMBAT TABLES

A quick glance at the progression of numbers on the [Attack Matrix Tables found in the Character Classes section or the attack matrix for Monsters] will reveal that 20 is repeated. This reflects the fact that a 20 (or above), even modified with bonuses “to hit”, indicates a “perfect” hit. It also incidentally helps to assure that opponents with high armor class values are not “hit proof”.

OPTIONAL RULE

Should any DM find that this system offends his or her sensibilities, the following modification is suggested: 

Consider the repeated 20 as a perfectly-aimed attack which does not gain any benefit from strength or magical properties of any sort — spell, missile, or weapon. That is, the 20 must be attained by a roll of natural 20. All bonuses accrue only up to and including a total of 20, so that even if a character attacked with a bonus for Strength of +3 and a +3 magic sword he or she would have to roll a natural 20 in order to score a hit on any creature normally hit by the second or successive repetitions of 20, i.e. the bonus (+3 in the example) could not exceed a total score of 20 unless an actual 20 is rolled. Thus, the [Attack Matrix tables] could be amended to read like this:

• 21 (natural 20 plus at least + 1 bonus)

• 20 (natural)

• 20 (natural)

• 20 (natural)

• 20 (natural)

• 20 (natural)

• 20 (die result + bonuses to total)

• 19 (die result + bonuses to total)

This then gives the advantage of allowing creatures to hit and be hit, yet it denies any undue advantages, as the second and all successive 20s, as well as all "to hit" scores above 20 require a natural die roll of 20.