Sisu TTRPG Rules

What is Sisu?

It is a Finnish word, but sisu is more than just a word; it embodies the spirit of resilience, determination, and perseverance in Finnish culture. It is pronounced "See-Soo".

Sisu is a tabletop roleplaying game (TTRPG) - a collaborative, imagination-driven experience you share around a table with friends. If you've never played one before, here's the idea: one person takes on the role of the Game Master (GM), who designs a world, sets the scene, and portrays the people and dangers the group encounters. Everyone else plays as a player character (PC) - a unique individual they've created with their own strengths, weaknesses, and personality.

There are no winners or losers. Instead, the group works together (or sometimes against each other) to navigate whatever situation the GM presents - whether that's a tense investigation, a desperate firefight, or a conversation with a shady contact. When you want your character to do something uncertain, you roll dice to find out what happens. You should not consider this game to be the players vs the GM, rather the GM is there to guide and facilitate an entertaining shared experience. The rules below spell out exactly how that works.

All you really need to play is this rulebook, some dice, a character sheet, and a group of people ready to tell a story together.

Creating A Character

Write your character name at the top of the portrait box. Write your title or profession at the bottom of the portrait box. Draw a picture of yourself and/or describe your looks in the portrait box.

Assign your character stats for Body, Mind, Sense, and Sisu by distributing d8, d6, d6, d4 for an already skilled character or d4, d4, d4, d4 for a non-skilled character (GM decides). Then select one stat to boost, going up by one die type. For example, d4 would become d6, d6 would become d8, and d8 would become d10.

The GM will say how much money you start with. Starting equipment can either be purchased or alternatively allowing each player to start with one weapon and one tool.

Fill in your armor value, ranging between 0 and 3, depending on what you have equipped.

Fill in your speed value in spaces. The default is 6, but can be different depending on character and equipment.

Fill in your max and current HP, which is default 10 (unless GM says otherwise). Max and current FP should match HP.

Select 2 skills (observing any prerequisites) and 1 flaw.

Ability Checks

Armor

Armor value is subtracted from any incoming damage. Total armor value can never go above 5. It is possible for armor to break and become ineffective. Armor may affect your speed.

Speed

In a single move, you can travel up to your speed value in square spaces (which are normally 5x5 feet or 1x1 meter). Your default speed is 6. Some environmental conditions, outside influences, or other modifiers may change this value.

Health Points (HP)

Damage causes you to lose HP and if you drop to 0, you are considered unconscious and dying. Unless you get healing to regain HP, you will die in 30 minutes. HP cannot go below 0.

A short rest (1 hour) lets you regain d4 HP. A long rest (6 hours) lets you regain all your HP.

Fatigue Points (FP)

Certain attacks, using skills or some strenuous activities can cause you to lose FP. Using a skill costs 1 FP unless otherwise stated.

If your FP falls to 0, at the start of each turn (during combat or other ongoing strenuous activity) you must make a BODY (4+) ability check or suffer 1 damage to HP. While at 0 FP, you also cannot use any skills. A short or long rest restores all FP.

Skills

Skills provide bonus modifiers for ability checks or combat. Every player starts with 2 skills, chosen as they wish. More skills may be added later when upgrading your character. You can apply a single skill benefit to each ability check you make if it makes logical sense. Use of a skill consumes 1 FP unless otherwise stated. New custom skills can be developed by the players but are always subject to approval of the GM.

Flaw

A flaw is something that may cause problems for the player. Every player starts with 1 flaw, chosen as they wish and approved by the GM. This flaw may change later or more may be added.

Inventory

A player may carry up to 9 items with the 10th item causing the player to become encumbered. Some items are tagged as "Bulky" and take up two inventory slots. The GM will decide what items are considered bulky. Being encumbered halves your speed while causing disadvantage on attack and ability checks. Some very small items take up no inventory space, and can just be noted outside of the inventory slots (at GM's discretion).

A Turn

A single turn consists of performing 1 move, 1 action, and 1 bonus action in any order. Actions often involve ability checks or damage checks. Bonus actions are things that are very quick to perform, like yelling a short phrase, making a hand gesture, switching/dropping a weapon, etc. Performing healing or standing from the prone position are considered full actions. Ultimately, the GM will determine if an action is considered bonus or not in the current situation.

Non-combat Turn

Players may announce what action they want to take at any time. Once a player starts explaining what they are doing, others must wait for the current player's turn to be finished, unless they want to hinder or assist them. A player may take multiple turns in a row if nobody else wants to take a turn. The GM may announce that an NPC or monster is taking a turn.

Combat Rounds

A single round of combat consists of everyone involved performing 1 turn, lasting 5 seconds (12 rounds per minute). The round includes all players and enemies involved in combat.

Initiative

Often it can be logically determined who is acting first in an encounter. Some characters may have skills that let them act first. In cases where turn order is not clear, all participants roll SISU die, highest acts first.

Ability Checks

Sometimes when a player wants to perform an action that may prove difficult, they will need to do an ability check by rolling the die they have assigned for that ability stat. You can also roll any equipment die that you have equipped and makes sense to use for the situation. You only choose the value of the highest rolled die (of all dice rolled). The GM will determine what value is needed to succeed. Depending on how much over or under your score is to the required success value, the GM may grant additional problems (if under) or bonuses (if over).

Advantage On Ability Checks

Roll two of the same ability dice (and any other equipment dice) and choose the result that is highest. All applicable modifiers still apply.

Disadvantage On Ability Checks

Roll two of the same ability dice (and any other equipment dice) and choose the result that is lowest. All applicable modifiers still apply.

Assisting Others (non-combat)

If it makes logical sense, the GM may allow another player to assist someone in an ability check, giving them a +1 or +2 bonus (GM discretion).

Hindering Others (non-combat)

If it makes logical sense, the GM may allow another player to hinder someone in an ability check, giving them a -1 or -2 penalty (GM discretion).

Attacking

As an action, players, monsters, and NPCs can attack other players, monsters, or NPCs. Once an attack is declared, a damage check is performed.

Damage Check

Players, monsters, NPCs and breakable objects can take damage against their HP.

Attacker rolls ability die roll (and any weapon dice) and choose the result that is the highest (after applying any applicable modifiers) and that becomes the damage value.

The target then rolls their associated ability die (usually BODY) and adds their armor value and any other modifiers for their defense roll.

The damage to HP taken by the target equals the attackers damage value minus the targets defense value.

Unarmed melee damage checks are always performed at disadvantage unless otherwise specified by a skill.

Advantage On Damage Checks

Roll two of the same damage dice (weapon or unarmed attack) and choose the result that is highest. All applicable modifiers still apply.

Disadvantage On Damage Checks

Roll two of the same damage dice (weapon or unarmed attack) and choose the result that is lowest. All applicable modifiers still apply.

Other Modifiers To Ability Checks And Damage Checks

If a player can explain why some action should require a modifier value to be applied and it makes logical sense, it is at the GM's discretion whether to allow it. For example, successfully applying poison to a blade may cause it to do +1 more damage this turn or cause the poisoned condition.

Short Rest

Taking a short rest requires 1 hour of relaxing activity. You regain d4 HP and all FP.

Long Rest

Taking a long rest requires 6 hours of sleep. You regain all HP and FP. If you do not have a long rest once every day, your FP will drop to 0.

Upgrading A Character

Whenever the GM sees fit, like at certain milestones or adventure completion, you may be allowed to upgrade your character. This will usually consist of at least one of the following:

1. Upgrade any ability die 1 level (max d12)
2. Gain a new skill (to a limit of 10 skills)
3. Suggest improvement to an existing skill (at GM discretion)

You may also be able to change your flaw if it makes sense to do so. In some cases, another flaw may be added. All upgrades are at the discretion of the GM.

Weapon Modifiers

Players may occasionally find improved weapons. Improved version of a similar weapon, go up a die level up to a maximum of d12. Very rarely, a weapon could be obtained that is d20.

Weapons can become worn or damaged, causing them to go down a die level or take a -1 or -2 damage penalty until they can be repaired. Armor can also become worn or broken and need to be replaced.

Example Equipment

Melee Weapons

Ranged Weapons

Armor

Miscellaneous

Conditions

Unless otherwise stated by the GM, all condition self-recovery ability checks are done at the beginning of each of your subsequent turns.

Lasting Wounds

Occasionally, a player may suffer a permanent or long-lasting injury from being involved in a major event or in place of death. The GM determines when these happen and if they are recoverable over time.

Example Skills

GM Hints

Setting Difficulty

When setting a target roll value to meet or exceed for a check, use this table as a guide.

Roll Results

When determining success or failure for a check, use this table as a guide.

Extra Resources

Online rules PDFs and character sheet - https://sisurpg.com/resources

Examples of play in fantasy and modern settings - https://sisurpg.com/exampleplay

Thanks & Inspiration

Sisu would not exist without the games that came before it. Several systems left a clear mark on its design, and credit is owed where it's due.

Dungeons & Dragons is the grandfather of the genre. The core vocabulary of this hobby - ability scores, hit points, armor class, conditions, skills, the GM/player split - all trace back here. If you've played D&D, much of Sisu will feel immediately familiar.

Tales From the Loop and Kids on Bikes both showed that a TTRPG doesn't need mountains of rules to tell gripping, character-driven stories. Their approach to keeping mechanics light and narrative central shaped how Sisu handles ability checks and the overall tone of play.

Cairn was a direct influence on inventory slots, the fatigue system, and the philosophy that rules should get out of the way of the fiction. Its elegant handling of encumbrance and resource pressure is something Sisu borrows heavily from.

Thank you to the designers and communities behind all four of these games.