Core Engine
One principle governs everything. Lower is better.
Every contested action — combat, magic, skills — resolves the same way. Subtract the opponents relevant attribute from yours, add 10. That is your target number. Roll a d20 under it to succeed. 1 is always a critical. 20 always fails.
When no opponent is present — climbing a wall, treating a wound, picking a lock — the GM sets a difficulty value instead. The formula remains identical: your skill minus the difficulty, plus 10.
KETU RPG is intentionally dangerous. Resources are limited. Positioning matters. The system is modular and setting-agnostic — the same engine runs swords, spells, and social manipulation.
Attributes
Five foundations. Ten expressions. All interconnected.
Every character begins with 3 in each of the five basic attributes. At creation, 4 additional points are distributed freely. The gap between your highest and lowest attribute cannot exceed 4.
Ten extended attributes are derived from the five basics. Each combines a primary (÷2) and secondary (÷3) source, rounded down.
Combat
Low HP. High stakes. Every round could be your last.
Characters begin with 1 HP, maximum 3. Reaching 0 HP triggers bleeding. Without stabilization within 3 rounds, death follows. A roll of 1–2 on d20 stops bleeding naturally. First Aid from an ally is safer.
Each round is 6 seconds. A character has 3 actions per turn. The same action cannot be used more than twice in a row unless Stamina is spent. Lower initiative rolls act first.
Attacker Close Combat − Defender Close Combat + 10. Roll under to hit. Both sides roll simultaneously — counterattacks are free and happen in the same exchange.
Resistance − (Weapon Strength + half Strength) + 10. Defender rolls under to resist. Fail → lose 1 HP. Critical hit adds +3 Weapon Strength.
| Weapon | Strength | Notes |
|---|---|---|
| Dagger | 2 | |
| Short Sword | 3 | |
| Rapier | 4 | |
| Mace | 4 | |
| Scimitar | 5 | |
| Long Sword | 6 | |
| Two-Handed Sword | 7 | Cost 2 Actions, +1 Close Combat |
| Great Axe | 7 | Cost 2 Actions, -2 Target Resistance |
| Maul | 7 | Cost 3 Actions, -2 Target Resistance |
Magic
Four elements. Unstable power. Costly mastery.
All magic flows from four elements: Fire, Water, Air, Earth. Magic is never guaranteed — it requires sufficient Stamina, a successful Mysticism check, and concentration. Failure means wasted Stamina at minimum.
Declare the spell and invest Stamina. Distribute it freely between Power, Range, Area, and Duration. Every 1 STA = 1 combat round or 10 non-combat minutes of duration.
Every 2 STA → +1 Power | Every 2 STA → +5m Range | Every 4 STA → +1m AoE radius
Actions required = ceil(Stamina ÷ 10). A 10 STA spell takes 1 action. An 11 STA spell takes 2 — and can be interrupted by a successful attack, requiring an Endurance check or losing all invested Stamina.
Spending all Stamina renders a character Exhausted — conscious but unable to move or act. Stamina recovers at 1 per 10 minutes. Powerful mages are formidable but fragile.
Character Creation
Few steps. Deep implications.
KETU RPG uses Jungian archetypes instead of alignment. There is no Good or Evil — only motivation and decision. Archetypes guide roleplay and character development but never restrict player choice. They evolve naturally through play.
Conditions
What happens when things go wrong. And they will.
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