Ultramicrolite20 Expanded Guide for Players & Game Masters


Ultramicrolite20 was originally conceived as Microlite20 boiled down even further. Ultramicrolite20 is ideal for when you have the roleplaying itch, but don't have your gamebooks or character sheets with you.

All you need is a blank piece of paper or note card to use as a character sheet, and a d20 or a dice-rolling app on your smartphone or tablet. However, having a couple extra pieces of scratch paper or another mobile device to take notes with is recommended, especially for campaigns that are longer and more complex.

This new expansion focuses on flexibility and versatility without adding too much or boiling it down any further. The rules are meant to be somewhat flexible, mainly in regards to giving game masters more of a blank canvas than a predefined setting and ruleset.

Even though Ultramicrolite20 was designed for simplicity, this expanded guide aims to allow for more types of games, including longer campaigns as well as campaigns that are more experimental.


Characters have four stats: Strength, Dexterity, Mind & Charisma

Characters get seven ability points to spend between the three abilities. Each ability point is a +1 bonus. The game master can set maximum ability bonus limits, as well as setting a minimum of +1 for each ability.

Optional: For games involving superhumans, demigods, interdimensional beings, cyborgs, and/or any other types of characters with extraordinary abilities may be awarded an extra one to three ability points as per the game master. Game masters should make sure to equally dole out bonus points if this is the case.


Characters have four skills: Physical, Subterfuge, Communication & Knowledge

Characters get seven skill points to spend between the four skills. Each skill point spent is a +1 bonus to that skill.

If the character survives ten combats or succeeds in ten skill checks, add +1 to all four skills. The game master ultimately decides if this award of skill points stacks and how to implement this effect. This could be seen as a simplified way of "leveling up" a character, akin to many other role playing game systems. Players can mark each skill increase as a level up on their character sheet, if desired.

Actions & Combat

Actions are resolved by rolling 1d20 + relevant skill bonus + relevant ability bonus. Roll equal or higher than given DC (Difficulty Class) or higher than opponent's AC to succeed.

Optional: The game master may give bonuses up to +2 or penalties up to -2 for specific actions, environmental effects, current state of the character, etc.

Initiative is determined using 1d20 + Dexterity, rolled at the beginning of combat. Combat consists of special action rolls:

Melee/Hand-to-Hand Combat If 1d20 + Physical + Strength + Weapon Bonus (if any) beats the DC or enemy's AC, it's a hit.

Examples: +1 bonus for brass knuckles and very small slashing/piercing weapons, +2 for small bludgeoning and slashing/piercing weapons, +4 for large slashing/piercing and bludgeoning weapons. Additional +1 for mastercraft weapons.

Projectile/Missile/Ranged If 1d20 + Physical + Dexterity + Weapon Bonus (if any) beats the DC or enemy's AC, it's a hit.

Examples: +2 bonus for pistols, +4 for shotguns and rifles without scopes, +6 for sniper rifles with scopes and assault weapons, +10 for bazookas/cannons. Additional +1 bonus for laser weapons.

Magic/Psionic/Supernatural If 1d20 + Knowledge + Mind beats the DC or enemy's AC, it's a hit. However, if the character is using music or some sort of a performance as part of the attack, use Charisma instead of Mind.

Social Combat If 1d20 + Communication + Charisma beats the DC or enemy's AC, it's a hit. If applicable to the situation, the Knowledge skill can be used instead of Communication.

Armor & Will

AC (Armor Class) determines the character’s defense against melee and ranged attacks.

AC is 10 + Dexterity + Armor Bonus (if any)

Examples: +1 bonus for leather, +3 for chain mail or bulletproof vest, +5 for riot gear, +10 for powered suit, +1 bonus for small shield, +2 for medium shield, +3 for large shield, etc.

Shields can’t be wielded with two-handed weapons.

Will determines the character’s defense against magic attacks and social combat. Will is 10 + (Mind x 2).

Health & Wounds

If a character is hit three times in a single physical combat encounter, they become unconscious. The player must make three successful death save rolls to survive. A death save roll is 1d20 + Strength + Physical. The DC for a death save roll is 15. Three failed death save rolls will result in the character’s death. Enemy characters and NPCs do not roll death save rolls.

Health can be restored by food, water, rest, medkits, potions, and other items at the game master’s discretion.

In social combat, a similar system is used. If a character suffers three social wounds, they have been outwitted. However, what happens next is up to the game master. Wounds from physical and social combat should be kept separate in most cases. One example of social combat that could result in physical wounds are charisma based magic attacks.

Hazards & Effects

Falling Roll 1d20 + Physical + Dexterity to beat DC (DC = feet fallen). A failed roll means the character suffers at least one wound, per the game master. If the fall is greater than 20 + Physical + Dexterity, the character suffers two wounds, unless the player can roll a natural 20, in which they only suffer one wound.

Falling (Spikes) Roll 1d20 + Physical + Dexterity to beat DC (DC = feet fallen) and suffer one wound. A failed roll means the character suffers two wounds, and the player rolls again to beat a DC of 15 for their character to stay conscious. If the player rolls a natural 20, they take no damage. If the fall is greater than 20 + Physical + Dexterity, the character rolls again to beat a DC of 15 to stay conscious.

Extreme Heat & Cold Without protection, 1d20 + Physical + Strength save every three turns (DC 15, +1 each roll after that). One wound for each failed save.

Poison Without immunity, roll 1d20 + Physical + Strength to avoid or reduce damage or any other effects. Effects and DC are decided by game master. If the player rolls a natural 20, the character gains immunity to the poison. Again, the effects of poison immunity are decided by the game master.

Illness Depending on type, either roll 1d20 + Will, 1d20 + Physical + Strength or 1d20 + Physical + Mind to avoid or reduce damage or any other effects. Effects and DC are decided by game master. If the player rolls a natural 20, the character is asymptomatic (no effects on character) and/or becomes immunized to the illness. Again, the effects of these are decided by the game master.

Psychoactives Depending on type, either roll 1d20+Will or 1d20 + Physical + Mind to beat DC. Like poison, effects and DC are decided by game master. Unlike poison, psychoactives could have positive effects on the character if the roll beats the DC. Addiction to psychoactives can cause wounds and penalties to stats as the character experiences withdrawal, as per the game master.

Version History

Published by KSBP, 2015-2021

Written by Stef

Ultramicrolite20 Expanded Guide Final Version (Restyled) – 26 Aug 2021 (HTML) ←You are reading this version. Ultramicrolite20 Expanded Guide Final Version – 21 Jun 2020 (Markdown/HTML) Ultramicrolite20 Expanded Guide First Version – 27 May 2017 (Markdown/HTML) Ultramicrolite20 Expanded Guide Final Draft – 20 Apr 2017 (Markdown/ODT) Ultramicrolite20 Expanded Guide Second Revised Draft – 23 Dec 2016 (DOC/ODT) Ultramicrolite20 Expanded Guide Revised Draft – 24 Feb 2016 (plaintext/DOC) Ultramicrolite20 Expanded Guide First Draft – 11 Nov 2015 (plaintext)

Design updated 26 Aug 2021

Source Material Ultramicrolite20 Revised Version by Domino Writing – 13 Sept 2015 (PDF) dominowriting.com/Ultramicrolite20Revised.pdf Microlite20 Purest Essence SRD by Robin V. Stacey, Darrell King & Al Krombach – circa 2008 (PDF) donjon.bin.sh/m20/Microlite20.pdf

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