The Stellar Alliance: Quantum Rules

Posted: 2023-09-23
Last Modified: 2024-03-12
Word Count: 2472
Tags: cepheus rpg settings

Table of Contents

Part of a series on the Stellar Alliance.

This game incorporates text from Cepheus Quantum by Stellagama Publishing. It is therefore licensed under the Creative Commons Attribution Share-Alike International License 4.0.

The Basic Game Mechanic

Throw 2d6: throw two six-sided dice and add the results together, add the skill modifier, and compare to difficulty. If the total equals or exceeds the difficulty number, you succeed. Otherwise, you fail. Skill notation: “throw Technical 6+” = throw two dice, add them together and add the Technical skill, and if the total equals or exceeds 6, you succeed. If you lack a skill, throw at -1 penalty (i.e., subtract 1 from the throw).

Task Difficulties

Difficulty Description Difficulty Number
Easy 4+
Average 6+
Difficult 8+
Formidable 10+


There are 6 skills:

Character creation

  1. Distribute 5 points among your six skills. You may not exceed 3 in any one skill.
  2. Choose one Trait from the list below or a new one with the Referee’s approval.
  3. Your Stamina is equal to 12 plus twice times your Physical skill. This represents your resistance to injury.
  4. Your equipment is at the Referee’s discretion.
  5. You may carry up to 10 Items plus two items per point in your Physical skill.
  6. Think of a description and a personality for your character.


A character begins with one Trait. Most Traits grant Advantage to throws that fall under the Trait. When a character has Advantage, the player rolls an extra die and counts only the highest two as his throw.

Common Traits

You get Advantage when piloting any form of starship or spaceship, or any atmospheric craft. You do not get Advantage on ground, water, or underground craft, only those that fly through air or vacuum.
Combat Medic
You get Advantage on all Knowledge throws to treat wounds and diseases in humans and humanoids, even in primitive or sub-optimal conditions.
Cyborg (Part)
You have an implant that either mimics some portable device or grants you an Advantage on a Physical or Combat throw using that body part. The Player and Referee should define the exact effects of the artificial Part when the Player chooses this Trait.
You get Advantage on all Knowledge and Technical throws related to computers, A.I.s, and other information technology. This includes attempts to circumvent or strengthen security restrictions.
You get Advantage on all Knowledge, Physical, and Technical throws related to movement in zero-G and extravehicular activities (E.V.A.) including how to don a spacesuit correctly, airlock ettiquette, and working in the vacuum of space.
Specialist (Subject)
You get Advantage on all throws related to Subject, defined when this Trait is taken. The Player and Referee should work on the domain and limits of the Subject.

Alliance Service Traits

A current or former member of the Alliance Exploration Fleet may choose one of these traits. To match their Service within the Fleet, their highest skill(s) should reflect their Service:

Service Includes Primary Skills
Command commanders Social
Medical doctors Knowledge
Operations pilots Physical, Technical
Science science officers Knowledge
Security security Combat, Physical, Stealth
Technical engineers Technical
Alliance Commander
You get Advantage on Social throws to inspire a crew, command a starship, or interact with members of a known alien culture or species. You also speak two additional languages (chosen at character creation) without using a translator.
Alliance Doctor
You get Advantage on all Knowledge throws concerning the biology of any known alien species, and the treatment of wounds and diseases in those species. You also get Advantage on all uses of medical equipment. When you encounter an unknown alien species you may take an educated guess: roll without Advantage, but reroll any die that comes up 1.
Alliance Engineer
You get Advantage on all Knowledge and Technical throws to analyze and repair spaceships, starships, or Alliance technology.
Alliance Pilot
You get Advantage to Technical throws to pilot any form of starship or spaceship, or when using technology in an Alliance starship or spaceship.
Alliance Science Officer
You get Advantage on all Knowledge throws related to science, technology, and existing research. You also gain Advantage on Technical throws when using computers and other standard scientific equipment. When you encounter an unknown phenomenon you may take an educated guess: roll without Advantage, but reroll any die that comes up 1.
Alliance Security
You get Advantage on all Knowledge throws related to security procedures within and outside the Alliance, and all Technical throws related to security technology and tools.



Armor Protection
Leather 2
Bulletproof vest 3
Ballistic Cloth 6
Space Suit 6
Combat Armor 11


Weapon DMG Range
Dagger 1d6 -
Axe or Machete 2d6 -
Two-handed sword or battleaxe 4d6 -
Sword or Cutlass 3d6 -
Handgun 2d6 10/50
Shotgun 4d6 20/40
SMG (Auto) 2d6 30/100
Assault Rifle (Auto) 3d6 50/200
Laser Rifle 5d6 300/500
Pulse Rifle (Auto) 4d6 300/600
Blaster 4d6 50/200
Hand Grenade (3m radius) 5d6 5/15

Stun Weapons

Weapon DN Range
Stun Baton 8+ -
Taser 8+ 5/20
Electrolaser 8+ 20/100
Sonic Stun Pistol 6+ 50/200
Exo-Carbine Stunner (gray market) 10+ 300/500


All Exo-Weapons have biometric security to prevent their use by non-Alliance personnel.

Form Range
Exo-Holdout (“buzzer”) 10/90
Exo-Pistol 90/-
Exo-Rifle 300/500
Exo-Cannon (tripod mount) 500/1000

Exo-Weapon Settings

Settings beyond Stun require security overrides from an authorized commanding officer or the issuing ship’s computer.

Setting DMG Range Special
Stun DN 10+ by weapon default setting
Cut 4d6 - meant to cut bulkheads, etc.
Burn 4d6 10/- meant to heat rocks, etc.
Kill 6d6 by weapon radiation damage, ignores armor
Disassemble 9d6 by weapon disintegration damage, immediate Triage


Vehicle Agility Armor
Ground Car +0 Unarmored
APC -1 Light
Helicopter +1 Unarmored
ATV -1 Light
Aircar +0 Unarmored
Grav Gunship +0 Heavy
Tank -2 Heavy
Motorcycle +2 Unarmored

High-Tech Gear

Type Description
Communicator, earpiece fits inside or around ear, integrated translator
Communicator, wearable badge or jewelry, camera, small computer, translator
Communicator, pocket small viewscreen, camera, computer, translator
Communicator, tablet viewscreen, camera, computer, translator
Communicator, relay brick-sized, extends communicator range
Multi-Sensor scans area for EM, heat, gravitic emissions

Personnel Combat

There is no initiative – everything happens simultaneously, and the results of combat actions (e.g. wounds) are applied after all combat actions are resolved.

In a combat round, you may move up to 10m and attack or move 20m without attacking.

Throw Combat 8+ to hit a target in melee or in ranged Effective range; Combat 10+ to hit beyond Effective range. Apply the target’s Combat skill as a penalty to hit. Shotguns can hit two adjacent targets at once (throw to-hit for each). Automatic weapons can attack twice a round (any target).

Stun weapons do not inflict Stamina damage. Instead, each has a Difficulty Number to avoid the stun effect. The character must throw Physical DN or fall unconscious until the end of combat. When combat is over, stunned characters will wake up groggy (or twitchy if the stunner used electric shocks) but otherwise whole.

For other weapons, upon a hit, throw the weapon’s damage dice, subtract any armor, and apply to the target’s Stamina. As long as Stamina is positive, the character is not wounded, only bruised. However, if Stamina runs out, the character is Wounded and typically is out of combat. Characters may attempt to keep fighting even when Wounded; throw Physical 6+ to keep fighting when receiving a wound.

Any further damage caused to a Wounded character causes additional Wounds. The character may throw Physical 6+ to keep fighting every time they receive a wound. However, every Wound the character suffers incurs a -1 penalty on the Triage roll, as well as to the roll to keep fighting when wounded.

When combat is over, characters with a positive Stamina recover their full Stamina within 10 minutes of catching their breath and resting. For each Wounded character, roll on the Triage table after combat. Apply -1 per Wound the character suffers; -2 if the character is attempting to recover on their own (without first aid); +2 if another character uses a medical kit on them.


2d6 Result
5 or lower Death
6-7 Severe injury; character will recover after 3d6 weeks of medical care.
8-10 Moderate injury; character will recover after 1d6 days of rest
11 or higher Flesh wound; character will recover within 1 day of rest or immediately with a medical kit.

Vehicle Combat

Vehicle combat is a chase and is played in turns. Each side throws 1d6 + Technical + Agility; the vehicle with the higher throw has Position. The Pursuer wins on ties. A vehicle with Position may attack normally (Combat 8+). A vehicle without Advantage can attack at a -4 penalty. Chase lasts until one side is disabled or 5 turns pass without either being destroyed.

Armor penetration depends on weapon and armor. Upon a successful hit, compare the vehicle’s armor to the weapon type on the following table. Then, refer to the appropriate Vehicle Damage Table.

Vehicle Penetration

Armor/Weapon Small Arms Support/Laser Gunnery
Unarmored Regular Regular Critical
Light - Regular Critical
Heavy - - Regular

A hit component is disabled or destroyed (Referee’s discretion). Knocked Out is out of combat; a Crew hit causes 3d6 damage to all crew and passengers; Destroyed is destroyed and causes 5d6 damage to all crew and passengers unless they throw Physical 8+ to bail out.

Vehicle Damage

2D Regular Critical
2-4 Breach Knocked Out
5 Cargo Knocked Out
6 Crew Knocked Out
7 Weapon Crew
8-9 Locomotion Crew
10 Electronics Destroyed
11 Power Plant Destroyed
12 Critical Destroyed

Spaceship Combat

Spaceships have Armor, Agility, and Weapons (number, type, damage).


Spaceship Armor Agility Weapons
Boarding Pod Unarmored -1 -
Capital Ship Armored +1 2x Missiles, 4x Particle Beams
Corsair Armored +1 2x Missiles
Commercial Transport Unarmored -1 2x Pulse Laser
Escape Pod Unarmored -2 -
Fighter Unarmored +2 1x Pulse Laser
Frigate Armored +0 2x Particle Beams
Merchant or Scout Unarmored -1 2x Pulse Lasers
Ship’s Boat or Yacht Unarmored +1 1x Pulse Laser
Shuttle Unarmored +0 -
Torpedo Boat Armored +1 2x Missiles, 1x Particle Beam
Tug Unarmored +0 -
Tug towing ship Unarmored -1 -

Spaceship combat is a chase and is played in turns. Each side’s pilot throws 1d6 + Technical + Agility; the spaceship with the higher throw has Position. The Pursuer wins on ties. A spaceship with Position may attack normally. A spaceship without Position can attack at a -4 penalty. Chase lasts until one side is disabled or 5 turns pass without either being destroyed.

Space Weapons

Weapon Power
Pulse Laser Light
Particle Beam Heavy
Missile Heavy, 2 rolls per hit

The gunner for each weapon throws Combat 8+. Upon a successful hit, consult the following table, comparing the weapon Power to the ship’s Armor.

Armor / Power Light Heavy
Unarmored Regular Critical
Armored Regular on 4+ on 1d Regular

Missiles are limited in number (Referee’s discretion); the defender, in lieu of an attack on the enemy, may attack a missile, destroying it on a successful hit. A hit component is disabled or destroyed (Referee’s discretion). Knocked Out is out of combat; a Crew hit causes 3D damage to all crew and passengers. Destroyed ships usually take some time to explode dramatically, so crews often have time to race to the life-pods.

Spaceship Damage

2D Regular Critical
2 Hull Breach Knocked Out
3 Power Plant Knocked Out
4 FTL Drive Knocked Out
5 Weapons Knocked Out
6 Maneuver Drive Crew
7 Fuel Crew
8 Cargo Hold Crew
9 Crew Crew
10 Computer Destroyed
11 Bridge Destroyed
12 Critical Destroyed

Star Travel

When traveling between planets or stars, the pilot rolls Technical 6+, modified by the ship’s Agility. On success, the ship arrives just on time. On failure, the ship arrives too late for the intended purpose.

If the exact travel time becomes important the Referee will state it. Alternatively the Referee may present a map of local star systems on a square or hex grid with a scale of parsecs or light years. Travel times between stars depend on the type of FTL drive.

Jump Drives

Jump drives teleport a ship from one star system to the next. Each Jump drive has a rating for the maximum distance it can cross in a single Jump, from 1 to 6.

Jump Rating Parsecs LY Ext. Time
1 1.0 3.26 2.7 hr
2 2.0 6.52 5.5 hr
3 3.0 9.78 8.2 hr
4 4.0 13.04 11.0 hr
5 5.0 16.30 13.7 hr
6 6.0 19.56 16.5 hr

While those aboard ship feel no passage of time, outside the ship about three hours pass per parsec Jumped.

After each Jump a ship needs at minimum a day to refuel, recalibrate, and test its Jump drive. Full maintenance requires about 1d6 days per Jump. If the ship does not take the full time or lacks the required facilities, the ship’s engineer must make a Technical 8+ throw for each rushed Jump. A failure means the Jump drive will not work without full maintenance. If the dice show a natural 2, the drive has misjumped, and the Referee will put the ship in a random star system, volume of space, or alternate universe.


Heroic and determined characters may develop their talents quickly and become living legends. To represent this, Cepheus Quantum offers an experience system.

Characters gain 1 XP per adventure. Every 5 XP, the character rises in Rank. When they gain a new Rank, they may choose one of the following:

A player character may advance up to four times in Rank (up to Rank 5). Most NPCs do not rise above the Rank 2; higher Ranked NPCs are rare and unique.