Rift Bomb

These pieces of Atlantean technology actually tear open a hole in the fabric of reality, transporting the area affected into another realm, such as Faerie, or Shadow, or the Abyss. It's believed that these were actually rift generators, but when set to overload, they are essentially weaponized portals.

Worse, rift bombs can be tinkered with so they don't open a rift to some supernal realm or Astral domain, but instead to the Outside. Which would allow in the eldritch abominations that lurk within those blind eternities, while also undermining the fundamental laws of reality around the blast site. In effect, it's a localized apocalypse...

Thankfully, none of the powers with access to a rift bomb have any desire to end the world by opening up a door for the Great Old Ones. It's hard to rule Earth if it's being torn asunder by the tentacles reaching down from the sky...

However, if some extremist faction or cult were to get a hold of a rift bomb and unleash it on a populated place, such as London or Tokyo, the devastation would make even the atomic bombs seem trivial...