Allods Online? Because there are apparently a lot of moving pieces at play. The latest article from the community team is penned by one of the game designers, and it explains extensively just what is involved in bringing a raid from the concept stage to the actual playable level.
For Allods Online, the first step is the writing team coming up with a concept for the raid that makes sense in the game world and ties into major figures. That leads to the creature and object designers getting a sense of how much can be done for any given raid -- how many new enemies can be created, how many bosses can be made, how big the maps can be. From there it's on to layout and battle mechanics. For a more in-depth overview, take a look at the full entry on the official site.