DooM: Fall of Mars starts out the same as Diablo: at a base where you can buy supplies, rest, and talk with some characters. However, all of the action takes place from within a lunar base, which has basically the same structure as the classic game Blizzard.
There, instead of skeletons, zombies, and other creatures from hell, you'll find some familiar enemies from Doom. Luckily, you'll have pistols, shotguns, machine guns, and other franchise-favorite weapons to fight them with. You'll also be able to find different types of armor and other defensive items.
DooM: Fall of Mars is an excellent role-playing game that will delight fans of both the Diablo and the Doom franchises, since it manages to perfectly combine the gameplay of one with the background and ambiance of the other.