War is a constant in many RPG’s. I believe that I have done enough war based adventures and campaigns that I might as well share some ideas and open the stage for others to share their thoughts.
A massive iron key - 2’ length, 20lbs forged from the bones and horns of demon-lords. When used with a massive portal - carefully built according to documents found in powerful books of evil knowledge, it will open into the realm of demons and allow them to flood into the world. The applications of this item for villains are obvious. Mortals touching this item directly will suffer very dire consequences.