The players are divided into two teams. One player takes on the role of the demons that have invaded a Marine space station. One to three other players control Marines in the base, which must secure a mission goal, primarily escaping the space station! The player controlling the demons chooses which of the scenarios provided will be played, and sets up the first room, placing the marines on their starting locations, and placing all other tokens that might be in the first room. Each marine player takes a reference sheet showing weapon and demon stats, and one marine equipment sheet. On the equipment sheet, the marine player places armor and wound tokens, and the shells and/or bullet tokens. A deck of marine skill cards gets shuffled and are dealt to each player. These cards represent the various skills the marines possess. The demon player takes a deck of invader cards, shuffles them, and draws five. All other tokens, monster figures, and boards are placed near the demon player to help set up the scenario. The marine’s take the first turn, and play alternates between them and the invader.

Each Marine turn, they may perform one of 4 actions. They can;

Sprint: moving up to eight spaces, but are unable attack. Marines cannot move through enemy figures, obstacles, or walls. Opening or closing a door costs two movement points, while giving a piece of equipment to another marine costs one movement point.

Advance: Move up to four spaces and make one attack. To attack, a marine nominates any enemy figure he can draw line of sight to. Then the marine selects a weapon he has ammo tokens for. note - some weapons do not require ammo. Next the marine rolls the dice indicated on the wepaon reference sheet. Once dice are rolled, the total distance is added up. If the total distance rolled is equal to or greater than the distance to the target, the marine has scored a hit. Add up the number of explosions to see how much damage the hit will do. Subtract the creatures armor and that is the amount of damage done. If any bullet silhouettes are face up on the dice, the marine loses one ammunition from the weapon used.

Unload: Make two attacks, but cannot move.

Ready: May attack OR move four spaces. The player then places one marine special order. The tokens are;
Aim - allowing the marine's attacks to be re-rolled next turn
Guard - allowing the marine to make one attack on the demon player's turn
Dodge - allowing the marine to force the demon player to re-roll any dice used in an attack on the marine
Heal - may only be used by a marine with the medic skill, allows the marine to heal one point of damage

After the Marines take their turn, the demon player draws one card for each marine in the game. The invader can then play one spawning card, placing the creatures shown on any space the marines cannot see. After spawning, the demon player activates all of the creatures onboard, moving and/or attacking with them. Demons move and attack just like the marines, but they may only do the advance order. The demon player may play cards from their hand whenever the card allows but only one spawn card, and only on their turn. Whenever a marine is killed or fragged, they keep any weapons, but reset all health and armor to the base value. The marine respawns in any explored space, eight to 16 spaces away from where they died.

Every time the marines enter a new room, the demon player sets it up, placing the enemies and equipment shown in the scenario booklet. Each new area has a bit of flavor text to set the scene. The demon player reads this aloud to the marines. The marine players must complete the mission requirements to win the game. The demon player must score six kills to win the game, and every time they draw the last card from their invader deck, it counts as a kill.

A word of advice:

Marines must stick together. Once the marines get strung out, they become very easy prey. Easy prey means quick kills for the demons and a short game for the marines.

Marines need to be quick and decisive. Every turn the demon are going to be spawning. Move through areas quickly but do not open a door until you have at least calmed the area you are in a fair amount. Nothing is worse than running from a horde of zombies and imps, and opening a door to find a hell knight staring right at you.