The Desolation Engine is magical device designed to annihilate anything in a mile radius. The ultimate weapon, it was invented by Kenspeckle Grouse in his youth while experimenting, just to see if it was possible. Grouse was later able to modify it to only activate when the user lets it go or to spare the user. The bomb was kept in The Irish Sanctuary until it was stolen by the Revengers' Club. The bomb has only been used three times (although one of these detonations was harmless as it was teleported to the ocean). It is described in the books as a stone hourglass,with green liquid that turns red when armed.
The Desolation Engine has three stages before it can be used. When the liquid is luminous, it means that it is live. When it turns red and starts to bubble, this shows that the bomb is armed. The final stage is when it is triggered and the bomb explodes.
The Desolation Engine was once used in 1498, in a town outside of Naples. Every living thing, building, tree and stone was obliterated. It was then kept in The Irish Sanctuary.
In the Books
The Revengers' Club stole it from the Sanctuary after Dusk raided it with Vampires. The Club then kidnapped Kenspeckle Grouse, the creator of the bomb, and used a Remnant to make Kenspeckle fix it, modify it, and create a second one. One bomb was recovered by Skulduggery Pleasant. The second bomb was modified so as to only arm when in the hands of Thurid Guild, and to trigger when it left his hand, while also sparing Guild's life. Dreylan Scarab planned to use the second bomb at Croke Park Stadium to kill 80,000 people on live TV. Scarab blackmailed Guild into blowing up the stadium up, with the threat of Billy-Ray Sanguine killing his family. Just as Guild was going to Detonate the bomb, Fletcher Renn teleported Guild to the sea, where the bomb killed many fish, but spared Guild's life.
The recovered bomb was used by Davina Marr to blow up the Sanctuary. Directed by the Roarhaven mages and the Man with the Golden Eyes, she used Myron Stray's True Name to force him to destroy the Sanctuary.