Strife is a Doom-like 3D action shooter and last game that had used the Doom engine. Although from the first sentence it may seem it will be just another copy of Doom, that's not what you should except. The game is set in a medieval environment and is not just about mindless shooting, but in the game you have to fulfill various tasks.
First things first. In the distant future the Earth is controlled by a group of people who call themselves "The Order" and they are trying to control all aspects of life. Of course the rebellion is formed, that is trying to overthrow this Order and free the Earth from all the terror. You are also part of to the rebels group and you have to accomplish several tasks given by different game characters. You won't just linearly proceed through the levels, but you can also decide which task you complete and this way you can modify the storyline a bit (game has a three different endings).