Overkill is a game system that allows players to fight skirmish battles in a fearsome futuristic setting. Players can design their own force of infantry and custom built vehicles or can select a command from one of the large number of units available in the "Sabotage universe". Whether it is a tough CPEC Marine company, a band of Acheron fanatics or a players own tailored force – all will be tested in the searing environment of Overkill.

The Overkill rules emphasise the careful deployment of troops, the effective employment of weapons and tactics, and the most efficient use of command and control. If players get this right, they have a chance of winning, but players must beware – as contact with the enemy is made, plans can go awry, control can break down and desperate chaotic fighting can result.

In addition to the game system, Overkill contains extensive background material for games and campaigns in the bleak "Sabotage universe". The action is centred around the rebellion that has once again flared on Mars and CPECs attempts to stamp its authority on this troublesome colony.