Microlite20 Old School Style

Microlite20 OSS

These are the core rules for an old-school flavored version of the basic Microlite20 (M20) rules. This rule set is designed to be significantly compatible with the d20 SRD. Please refer to the SRD for details on things not fully elaborated upon here, including equipment and spells. No rules, however, trump DM fiat in the pursuit of a good story.


There are three basic stats in M20: Strength (STR), Dexterity (DEX), and Mind (MND). Roll 4d6 three times, and drop the lowest die from each roll. Then assign these rolls to your three stats as you wish.

Each of these stats provides you a stat bonus equal to (STAT-10)/2, rounded down. This stat bonus is applied to dice rolls relevant to the stat in question.


The four races of M20 are Humans, Elves, Dwarves, and Halflings. Humans get a +1 to all skill rolls (see below). Elves get a +2 to MND. Dwarves get a +2 to STR. Halflings get a +2 to DEX.


Characters in M20 may be Fighters, Rangers, Rogues, Clerics, or Magic Users.

Fighters may wear any kind of armor and may use shields. They add +1 to all attack and damage rolls; this increases by an additional +1 at 5th level, and at every five levels thereafter.

Rangers may use light or medium armor, and may use shields. They get a +1 to hit and damage with ranged weapons, which increases by another +1 at 5th level and every five levels thereafter.

Rogues may only use light armor. If a rogue successfully sneaks up on an enemy he may make a backstab attack and add his level to the damage done on his first attack. Rogues have a reduced penalty when attacking with two weapons.

Clerics may wear light or medium armor, and cast divine spells. They may attempt to Turn Undead 2 + level + MND bonus times per day. When turning, a magic attack is made against a DC of the current hit points of the targeted undead; if this DC is exceeded by 10 the target is destroyed.

Magic Users wear no armor. They cast arcane spells.


Players select at creation a brief (two to three word) character background that represents a broad base of skills, knowledge, and abilities (eg, “eccentric artist”, “hedge knight”, “ambitious former slave”). These backgrounds need not be related to the PC’s class. The DM considers these backgrounds when deciding upon whether a character succeeds at an action and may assess bonuses or penalties accordingly.

Skill Rolls

M20 has no skills, per se. Rather, players are expected to think like adventurers and describe to the DM what their PCs are doing; the DM may decide immediately upon the success or failure of an action, or may request a skill roll.

For an action that is directly related to a character’s class or background, make a Primary Skill Roll equal to 1d20 + the relevant stat bonus + the character’s level.

If the action is loosely related to a character’s class or background, make a Secondary Skill Roll using half of the character’s level, rounded down, in the above formula.

If there is no relevant connection to the character’s class or background, make a Minor Skill Roll using one third of the character’s level, rounded down.

The DM will specify any additional situational modifiers and a target DC. If the DC is exceeded, or a natural 20 is thrown, the action is a success. Outcomes may vary depending on the degree of success or failure.

Saving Throws

A saving throw is rolled much like a skill check. For any saving throw, roll 1d20 and add your level, plus your STR bonus for a Fortitude Save, your DEX bonus for a Reflex Save, or your MND bonus for a Will Save.


Magic Users can cast any arcane spell, and Clerics any divine spell, with a spell level of no more than ½ their level, rounded up. See the d20 SRD for a full spell list and descriptions. Spells need not be memorized in advance. The DC of all spells is 10 + caster level + MND bonus.

Channeling magical energy is extremely tiring to the body and mind. Casting a spell costs its caster 1 + double the spell level in hit points. This loss represents the fundamental mental and physical damage that reshaping reality does to a mortal body and cannot be healed by magic. They are, however, recovered after a full night’s sleep.

[NB: for further clarifications on casting damage and recovery, see here]

Characters may select one signature spell per spell level that they wish to use more than any other. This spell always costs 1HP less to use.


Combat in M20 is hazardous – as it should be! All PCs start with hit points equal to their STR stat plus 1d6. They gain an additional 1d6 HP per level. When a PC’s hit points reach 0 he is unconscious and close to death. From this point on, all damage directly reduces STR. When STR reaches 0 a character is dead.

Damage is healed at a rate of 1 STR point, or double the character’s level in hit points, per day of full bed rest. A night of rest will allow a character to recover 1HP from damage and all hit points lost to casting spells. STR lost to damage must be recovered before HP can be.

A character’s Armor Class is equal to 10 + DEX bonus + armor bonus. See the SRD for armor bonuses.

At the beginning of an encounter, the DM may at his discretion roll 1d6 for one or both sides. On a roll of 1-2 the side is surprised and may not act at all in the first round.

Players roll 1d20 and add their DEX bonus for initiative order. Each PC may do one thing per turn: move, attack, cast a spell, etc. Anyone not surprised and with a ready weapon who is not already engaged in melee combat gets an attack of opportunity against any opponent trying to move past them.

For each attack the player rolls 1d20 and adds the PC’s level, plus a relevant stat bonus: STR for melee attacks, DEX for missile attacks, or MND for magic attacks. If the number rolled exceeds the target’s AC the attack hits. A natural 20 always hits and does maximum damage; a natural 1 always misses.

If the total attack bonus is at least +6 and the combatant manages to drop or slay his opponent in melee he may immediately make a follow-up attack against any other opponent within melee range. This may continue indefinitely as long as he drops a new foe with every attack.

Fighters, rangers, and rogues may use their DEX bonus instead of their STR bonus when attacking with a light weapon or a rapier. They may also wield two light weapons at the same time and attack with both at a -2 penalty to each attack; for rogues this is reduced to -1.


Characters earn Experience Points when their party defeats enemies; note that enemies may be “defeated” without being killed. The number of XP given for any type of enemy is equal to that enemy’s hit dice; if more than one of each enemy type was defeated, increase the XP given by +1 for each doubling. For example, one kobold (a 1HD monster) would give 1XP; two would give 2XP; four would give 3XP; and so on.

Characters can also be given bonus XP for solving puzzles or other significant plot events, or for spending their ill-gotten gains in frivolous ways – wine, women, expensive hobbies, or anything that gives them no other direct benefit. 1XP may be given for each 100GP spent in this way.

When a character’s XP total is equal to 25 times his next level he may advance. Reset the XP total to 0 after each advancement. Each new level gives 1d6 HP and +1 to all attack rolls. At all levels divisible by three grant the PC an additional +1 to STR, DEX, or MND. At levels divisible by 5, fighters get an additional +1 to all of their attack and damage rolls, whilst rangers get a +1 to their missile attack and damage rolls. Clerics and Magic Users get additional spells at odd-numbered levels.

Microlite20 Old School Style

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