There is a new Forgeworld expansion for Warhammer 40k hitting today. Zone Mortalis. Here is an excerpt from the rules, and the link to them. They look at first glance to be a lot of fun.
http://www.forgeworld.co.uk/Downloads/Product/PDF/Z/zonemortalis.pdf
http://www.forgeworld.co.uk/New_Stuff

via Forgeworld
The following rules expansion for Warhammer 40,000 deals with some of the most savage arenas of combat conceivable, the battlefields the Codex Tactica Imperialis refers to as ‘Zone Mortalis’ — the fatal ground. Such zones be they the contested decks of a void warship, tangled mine works, lightless underhives, the prison-vaults of sundered fortress citadels, labyrinthine industrial sewer systems and sacred catacombs, all have a confluence of factors in common such as close-confinement, limited access for attack or escape routes, as well as treacherous environments, which make them murderous venues for warfare.

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