Evil Spirits

After Amanda's comment I decided to do a quick check for evil spirits, vampire ghosts, and other cockamamie supernatural creatures floating around my secret lair. No wonder the Good Guys have been able to sneak in so easily, it's like Times Square on the astral plane around here. It looks like most of my dead henchmen have been hanging about, and not only that but all the native spirits have been attracted by the unusual concentration of ectoplasm... it's like leaving your trashcan uncovered: next thing you know you've got stray cats in the kitchen and coons in the attic.

And of course there's at least half a dozen superheroes out there who can talk to ghosts.

Firecrackers only clear them out temporarily. I'm developing ghost-sensitive exploding leeches to scare them away automatically, but I've been having a problem with the leeches' own ghosts setting off chain reactions in the breeding pools.