Maby a second storyline or just a sidequest-line where you have to find and Stop a evil Scientist who want to take over the universe. You have to search in (5) Laboratorys (Spoiler! He is in the last one !reliopS) and you have to fight his creatures and Mutants till you have to fight him (hes anykind of half-human half-monster) and you have to find loot. And maby there will come more (Spoiler! he has a master?? !reliopS)
Or he (the master) found a power sorce of the Ancients and now uses the destruction by the ruin to take over the universe with his servant (the scientist) and his Mutants/Monsters