Lo! The Old Ones are returning to this realm, dear reader. The mind cannot possibly comprehend the sinister forces at work, but unearthly beasts have been discovered in the crumbling ruins of Philadelphia’s Navy Yard.

And no, it’s not Gritty.

The multitudinously tentacled post-industrial people eater is, in fact, an inflatable installation—but still probably evil!—summoned by U.K.-based artists Filthy Luker and Pedro Estrellas, working with local art collective Group X and Navy Yard operators PIDC. The surprisingly detailed sculpture, titled Sea Monsters HERE, features 20 tentacles stretching up to 40 feet, transforming the warehouse into a nightmare factory just in time for Halloween. Luker and Estrellas describe their work as a “personal vendetta against the mundane confines of the city in a heroic effort to make the world a brighter, more surreal place for us all.” This isn’t the first time the inflation installation artists have activated architecture with beastly appendages, and it surely won’t be the last.

Sea Monsters HERE is on view at Building 661 (13th Street & Flagship Ave) in the Philadelphia Navy Yard through November 16.