Mysterons from Dimension X have begun to attack ships at random. It is up to the PCs to figure out what they want, and how to stop them. The terrorist tactics of the Mysterons are similar in style to the X-Com computer games, the Captain Scarlet television series, and the series UFO.

Invasion of the Mysterons is a metacampaign. You add it to an existing campaign to make it harder, possibly in addition to using plot twists, hazards or personalities. Having Mysterons invade the current campaign is worth -4MD.

The Mysteron campaign essential extends all missions in an existing campaign by up to 12 rounds at most, the average being an extra 6 rounds. It also increases the deadliness of the campaign but compensates that with heroic characters which can obtain the potential for immortality.

• Nefarious. Missions involving working out what the overall plan of the Mysterons is. The victory mission for this type involves discovering the one weakness with which all Mysterons can be destroyed.
• Dastardly. Missions that are responses to terrorist acts of the Mysterons. The victory mission for this type involves destroying their main incursion point into our universe.
• Insidious. Missions where one or more major NPCs or PCs are Mysteron agents. The victory mission for this type involves infiltrating the main Mysteron base with undercover PCs.
• Diabolical. Missions that are about the technology of the Mysterons. The victory mission for this type involves hijaking a new prototype Mysteron ship.

Due to the mysterious and ineffable nature of the Mysterons, once you have started this campaign in an existing campaign, and have determined the two missions that will be offered to the heroes to choose from, determine what Mysteron mission type they are randomly.

Rewards for succeeding in at least three missions of the same type.

• Nefarious. Heroes: Damage to Mysteron agents and Invulnerables is doubled for the heroes.
• Dastardly. Heroes: +2 to all requisition rolls.
• Insidious. Heroes: Heroes are now able to detect Mysterons if they are adjacent.
• Diabolical. Heroes: One special item of the heroes' choice.

• Nefarious. Mysterons: Two ships or two deaths may now be turned into Mysterons in a mission.
• Dastardly. Mysterons: A Mysteron agent breaks MD/2 random modules on the heroes' ship before each mission just after the upgrade phase (dastardly invisible bombs).
• Insidious. Mysterons: All Invulnerables lose their Mysteron powers and become normal heroes.
• Diabolical. Mysterons: One special item that the heroes have no longer affects Mysterons.

The first mission in the Mysteron campaign is a “Kobayashi Maru” mission. Start the Invasion of the Mysterons in a regular mission of a regular campaign in which there is a ship of equal or greater size to the heroes' ship that ends up being destroyed. Bring it back as a Mysteron ship intent on blowing up the hero ship. If need be, a bot or NPC on the heroes' ship becomes a Mysteron agent (if one has been killed or destroyed) and prevents them from entering Hyperspace. The heroes' ship is eventually destroyed and all characters killed by the overwhelming might of the Mysterons. One clone is now a Mysteron agent and must attempt to sabotage every mission involving the ship. if the ship is destroyed while they are on it, they become an Invulnerable. If they enter Dimension X while still an agent, due to Ineffability - the player must create a new character.

The first ship destroyed, and/or the first non-hero being killed in a mission is resurrected by the Mysterons as one of their own. Place a Mysteron Marker on it. The ship or character resurrects 1D6 phases after death/destruction. It comes back in the same location or as near as it can get with full health - as good as new.

Mysteron starships have the following powers-

• Retro-metabolism
  Mysteron ships repair Size D6 of hull damage each round. Mysteron modules remove a damage marker on a D6 roll of 4+ each phase.
• Dimensonal Transcendance
  Mysteron ships cannot be boarded, docked with or teleported into.
• Ineffable
  Every round add 1 to the ships Ineffability score. Roll 2D6 and add the Ineffability during the round's bookkeeping. If the score ever exceeds 12, the ship enters Dimension X and does not reappear in the mission.

Mysteron agents have the following powers-

• Retro-metabolism
  Mysteron agents gain 1d6 HP at the end of every round, up to their initial hit points. No matter how big a minus they are at. They are never subject to radiation hazards, disease or loss of life support. At the end of every round, all broken equipment they are carrying is repaired. However if they spacewalk without EVA they immediately become incapacitated until the end of the mission. The character may never use cyberwear.
• Dimensonal Transcendance
  No scan or science check will ever detect if a character is a Mysteron agent.
• Ineffable
  Every round add 1 to the agents Ineffability score. Roll 2D6 and add the Ineffability during the round's bookkeeping. If the score ever exceeds 12, the agent enters Dimension X and does not reappear in the mission. If a previously heroic character enters Dimension X, they permanently become a Mysteron agent (and NPC) - make a new character. This ex-Hero may turn up as a Personality in later missions.

Invulnerables are Mysteron agents who have regained their own personality - it only occurs to heroes who are Mysteron agents and are killed when their ship explodes. Invulnerables have the following powers-

• Retro-metabolism
  Invulnerables gain 1d6 HP at the end of every round, up to their initial hit points. No matter how big a minus they are at. They are never subject to radiation hazards, disease of loss or life support. However if they spacewalk without EVA they immediately become incapacitated until the end of the mission. The character may never use cyberwear.
• Mysteron Immunity
  Invulnerables are immune to all Mysteron mind control powers and may never become a Mysteron agent again.
• Ex-Mysteron Senses
  Invulnerables can detect Mysteron agents that are within the same module as them. Line of sight is not needed.
• Heroic
  If a mission ever ends when an Invulnerable is “killed” they are always retrieved during the book keeping part of the campaign turn, although their equipment isn't.

Weaknesses need to be discovered in order for the heroes to succeed against them in any mission. This may mean that more than the first mission involves everyone dying. These special items may replace those in an existing mission, or may be used as Prototype Weapons in the Overwhelming Success rewards table.

• Dimensional Stabiliser
  This cargo bay item allows teleporters to penetrate into a Mysteron ship with -6 difficulty.
• Retro Cognitive Dimensional Stabiliser
  This double sized carbo bay item allows teleporters to penetrate into a Mysteron ship with -3 difficulty.
• Portable Dimensional Stabiliser
  This item is about the size of a character and can be carried using the “Carry the Fallen” action. If loaded on a fighter, escape pod or boarding missile it takes up 1 crew space and allows the vessel to board or dock with a Mysteron ship.
• High Voltage Missiles
  High voltages stop retro-metabolism. These missiles automatically break the module they hit, cause 1D6 hull damage and cause 1D6 damage to all occupants inside. If the occupants are Mysteron agents or Invulnerables - this damage cannot be healed with retro-metabolism. Modules broken with these missiles cannot be repaired with retro-metabolism (but may still be repaired by engineers normally). Hull damage cannot be repaired with retro-metabolism.
• High Frequency Voltrex
  This modification to the standard Voltrex rifle in Galactic Civil Wars allows it to damage Mysteron agents (and Invulnerables) and the damage cannot be healed with their retro-metabolism (but may still be healed normally with a medkit).
• High Frequency EMP
  This modification to the standard EMP grenade and guns allows it to damage Mysteron agent equipment and the equipment cannot be repaired with their retro-metabolism (but may still be repaired normally with a toolkit).
• Understander Mk 2
  This upgraded Macroscope from Pax Galacticum can detect Mysteron agents.

If the heroes ship is destroyed and all Heroes killed (or in the case of Mysteron agents, temporarily killed) then three things happen-

1. One of the normal heroes will become a Mysteron agent.
2. Any hero that was a Mysteron agent before being killed becomes a hero again - but with Mysteron powers (an Invulnerable).
3. Any hero that was an Invulnerable is not cloned, but comes back as they were, but without equipment. Which means they earn XP, credits and prestige from the mission but not the bonus prestige for dying.