Introduction and Basic Rules

Introduction

M.O.S.S. is a game where adventurers fight monsters in the primordial landscape of Ohimyu. This is a world where powerful individuals serve as champions of the divines to enact their will on the surrounds.

All but one of the players of M.O.S.S. are playing as adventurers, or Player Characters (PC), characters of their own creation within the world of Ohimyu. The player takes on the role of this character within the world, describing how they react to situations and pursuing the goals which best fit the character's motivations. Most new players will initially make characters who are very similar to them in both manner and motivation, but more experienced players often find enjoyment in portraying adventurers very different from themselves.

The last player takes on the role of the Game Master (GM). The GM plays the character of Ohimyu itself. They are responsible for creating challenges for the PC's to overcome and rewards for doing so, monsters and non-player characters (NPCs) for the PCs to interact with, and describing the world of Ohimyu as it unfolds around the adventurers and reacts to their actions.

M.O.S.S. is played through players describing their character's actions in the world, and the GM describing the consequences of those actions. A series of actions and consequences form an encounter, defined as an obstacle to the adventurer’s achieving their goal. A series of encounters forms an adventure, the collection of related challenges opposing the adventure’s larger goal. And the total of all the adventures experienced by the players and PC’s forms the overall game and story.

When a player describes their actions, they must include both the desired outcome and the approach they use. This allows the GM to determine the affect this produces in the world. If they decide the action cannot succeed with the method chosen, it is automatically a failure, though lenient GM's might decide to warn the other player of the consequences first. If the GM decides the action cannot fail, or that it can fail but their is no meaningful penalty for repeated attempts, the action is a success. Only when the action could succeed or fail and there is a cost to repeated attempts does the GM refer to the Central Mechanic to determine the outcome.

The Central Mechanic

The Central Mechanic of M.O.S.S. is the Ability Check. The primary measure of the relative strength and weakness of creatures in Ohimyu is their six Ability Scores. When an action requires an Ability Check, the GM determines which of the six Abilities best governs the success of the action, and how difficult the action is to perform. The Difficulty of the task is the number of successes required to achieve the desired aim.

When players make an Ability Check, they roll a pool of d20's equal to that Ability Score. Every roll of 10 or higher counts is a success. As a character grows they may gain Mastery in certain actions. For each level of Mastery the player removes one die from their pool and replaces it with one automatic success. Characters may also gain temporary Boons and Banes. Boons are situational bonuses that increase the dice pool for an Ability Check, while Banes decrease the dice pool. Boons and Banes are subtractive of each other.

If PC meets the required number of success, the check is considered a total success. Otherwise it is either a partial success or failure, according to the GM's discretion. If the action succeeds or partially succeeds the PC either achieves their goal or makes progress towards it. If not they do not accomplish their goal and suffer the cost of failure. Regardless of the outcome, the GM describes the results and the consequences that occur because of the action.

Ability Scores

The Central Mechanic of M.O.S.S. is the Ability Check. The six ability scores measure the basic capacity of creatures in each of those six domains and determine the number of die rolled whenever a creature makes that kind of check. The six ability scores and their descriptions are detailed in the sidebar.

When PC's take an action, they are either attempting to overcome a feature of the environment or another creature or NPC. When they are working against the environment (jumping a ledge, picking a lock, identifying a rare plant) the GM determines the Difficulty (number of successes required) for the task, and any relevant Banes and Boons based on the situation. When they attempt to overcome another creature, the Difficulty is preset to the target's Ability Score, so a high ability score both makes it easier to accomplish tasks and it makes it harder to be overcome. It is always the creature attempting an action which rolls the check. For example, the Difficulty for a sneaking creature is the guard's Perception Score, while the difficulty for finding for finding a sneaker is the hiding creatures Agility Score.

Vitality

Vitality is a secondary ability that measures a creature's hardiness and is used whenever a creature's life is threatened. The most common use for Vitality is during combat, where a creature hit by an attack must succeed on a Vitality check to avoid succumbing to the blow. Poisons and diseases also trigger a Vitality Check, which must be succeeded or the creature is affected by the illness. The Difficulty for resisting a weapon, poison, or disease is called it's Lethality. A creature can also hold their breath for Vitality minutes before falling unconscious, and has Vitality minutes while unconscious to be saved before dying.

Lumen

Lumen is a secondary ability that measures a creatures available pool of magical energy. When someone tries to tap into the elemental forces of nature to produce magic, either on their own or with direction from their patron deity, they make a Lumen Check. Uniquely, Lumen Checks do not use d20's, instead they start with d4's and increment by one for every level of training they have in magic. Read Magic in Ohimyu for more on how the magic of this world works.

Understanding Dice

If you are new to Tabletop Roleplaying Games, you need to know how the dice work. In the TTRPG world, dice are referred to by the number of dice and number of sides on the dice. So d20 refers to twenty sided dice in general, while 2d6 would specifically refer to using 2, six sided dice. Nearly all dice rolls in M.O.S.S. use a d20, but there are a few specialized circumstances where others are used.

List of Ability Scores

• Agility: Agility measures the body control of the character
• Dexterity: Dexterity measures the hand control of the character
• Strength: Strength determines the physical power of the character
• Faith: Faith determines the mental power of the character
• Perception: Perception governs a characters awareness of the world
• Knowledge: Knowledge governs a characters understanding of the world

Spending Dice

If you are about to fail an Ability Check, you can instead "spend" a die to succeed. By doing this, you also temporarily reduce your Ability Score by 1, removing a die from your pool for all future Checks. You can, in theory, spend die on all Ability, Vitality, or Lumen Checks, and can spend die until you have a score of 0, at which point you automatically fail any Checks of that type. You regain 1/4 of your total die pool each night resting, though this can instead be regain one die at a time through one hour rests throughout the day.

Simplified Rules

In order to play M.O.S.S., all players must play by the rules in this first section of the rulebook. The rules found in the following sections are used to give additional structure to the game for both players and Game Master, especially as pertains to the three modes of play. Your play group may also decide to reject or avoid specific portions of the rules that pertain to specific modes of play, and only use these simplified rules instead. That is also permitted, as long as everyone at the table is aware of and agrees to that decision.