The rules for the cultists are drawn from the Imperial Guard Codex, but the cultists could be represented by a number of different armies. Tau, Imperial Guard, Eldar and Dark Eldar are all good choices. Just choose appropriate models to represent each unit type.
The mission isn't designed to be "fair" for the cultist player. His job is to control the hapless NPCs. In all likelihood his forces will be wiped out before the end of the game.
As a final note, you can play this scenario without a GM. The rules for the cultist behavior are pretty straightforward. Just use the optional triggers for the warp fluctuations.
After the pacification of Attika III, it was discovered that a cult in the remote regions of the planet had escaped being granted the divine light of the Emperor. It was only by analyzing records and rumors of the conquered civilization that the logicians and cogitators were able to eventually piece together the cult's whereabouts. They were completely invisible to all electronic methods of detection. How this was possible was a question the Inquisition was eager to answer. At the same time, followers of chaos were being drawn to the same region, searching for an artifact that was calling out to them through the warp.
Force Organization: Each team creates a 1000pt army according to standard force organization chart.
The game master puts together a 500 points of cult force units chosen from the following list: Conscripts, Infantry Squad, Psyker battle squad, Penal Legion Squad and Ogryn Squad. No unit options may be chosen. This includes close combat weapons, heavy weapons, special weapons, vehicles and transports. Additionally the cult player gains a Primaris Psyker, at no points cost, who will act as the army's HQ. Do not purchase any wargear for this character. The Primaris Psyker loses Independent Character, and gains Eternal Warrior.
If more than three people are playing, the points limit should be increased, but the cult force should be about 500 points less than whatever each team is using.
Setup: Terrain should be placed in a manner agreeable to all players. The cult player has final say on any disagreements about terrain.
The cult force deploys first. The cult player picks a short table edge. Each cult unit must be deployed within 24" of this table edge, and at least 12” from the long table edges. No Cultist units may be placed in reserve.
The opposing teams then dice off. The winner chooses a long table edge, deploys first and gets the first turn. Each player's deployment zone extends 12" from their table edge. No units may be set up closer than 24" from any cultist unit.
After deployment the second player may attempt to seize the initiative. The cultist player goes last in turn order.
Special Rules:
The Primaris Psyker represents the cult leader and is a valuable resource. The artifact he holds is precious to everyone and cannot be lost. No unit may target the cultist Primaris Psyker with shooting attacks. Additionally, he considered to be constantly under the effects of the warp time psychic power (reroll failed to-hit and to-wound rolls in close combat). He has a 4+ invulnerable armor save and a Warp Lightning attack (Range: 18", S4, AP3, Heavy3). He is immobile and may not be moved by any player for any reason.
Cult forces are crazed and fanatical, ready to lay down their lives to protect the artifact and its master. For the purposes of this scenario all units in the cult force are fearless as long as the cultist Primaris Psyker is alive.
Cult forces are not well trained. They must always shoot at the closest enemy unit they can legally target even if they have no chance of affecting their target.
Warp Fluctuations - At the beginning of each cult-player's turn, if there is at least one cult model on the table, the cult player can choose to use one of the following abilities. Each ability may only be used once in a game, and only one ability may be used per turn.
- Warp Conflagration – Each non-cult unit within 12" of the artifact bearer takes D6 S5 AP- hits. These hits are applied even if the unit is in close combat. Units that suffer a casualty from this attack must immediately take a pinning test. If the bearer is part of the unit, the unit he is with is hit, but wounds may not be applied to the bearer. Optional Trigger: Activate Warp Conflagration on any cultist turn where there is an enemy within 8" of the artifact bearer.
- Gifts of Chaos – Pick a cult-force unit (except the Primaris Psyker). Remove all models from the unit and replace them with up to 5 chaos spawn models (do not place more chaos spawn models than there are remaining members of the unit). If the unit was in hand to hand combat place the spawn so that they remain in contact with the unit(s) they were fighting. For the rest of the game the spawn move and fight as a single unit. Optional Trigger: Active Gifts of Chaos the first time a cultist unit charges or is charged.
- Warp Pulse – Every non-cult unit is pushed back so that they are a minimum of 6" away from the cult leader. If the unit was in close combat they are no longer in close combat. Move the units in a straight line away from the cult leader, taking dangerous terrain tests as normal. Any unit moved in this manner immediately takes a pinning test. Optional Trigger: Activate Warp Pulse on any cultist turn the Primaris Psyker is locked in close combat.
The cult leader starts out as the artifact bearer. Any model that kills the artifact bearer in close combat gains control of the artifact and becomes the artifact bearer. While that model is the artifact bearer it cannot be targeted by shooting attacks. The player with control of the artifact at the end of the game wins. The game length is random. At the end of turn 5 the player controlling the artifact bearer rolls a die. The game continues on a roll of a 3+. Roll again at th eend of turn 6, continuing on a 4+. The game automatically ends after turn 7.
When the artifact is taken from the cult leader, it is possible that it will be taken by a squad. If it is taken by a squad or an independent character that is part of a squad, designate a single model in that squad as the artifact bearer. This model is the one that must be killed to take the artifact. The unit the model is part of may still be the target of shooting attacks, but wounds from shooting attacks may not be allocated to the artifact bearer.