You choose between the Divine Path of Obedience (playing as an angel) or the Fallen Path of Power (playing as a demon).

Because these games are now considered "retro" or "abandonware," they aren't on modern stores like Steam, but you can find them through preserved archives: The War In Heaven Review for PC - GameFAQs - GameSpot

The Strange Case of "War in Heaven - 1917": A Forgotten PC Relic?