Horace Slughorn used it on a Muggle-owned house he stayed in temporarily in 1996 in Budleigh Babberton, but did not hear it go off when Albus Dumbledore and Harry Potter arrived because he was in the bath.
Behind the scenes
- The Intruder Charm might be the given name of the spell Cave inimicum, given the latter's etymology.
- The Caterwauling Charm could be a long-range version of this charm since it was loud enough to alert the Death Eaters and all the villagers when the trio came into Hogsmeade.
- Harry Potter and the Half-Blood Prince (First mentioned)
- Harry Potter and the Deathly Hallows: Part 2 (Possible appearance)