I like antagonist spirits <3 Have some ideas I can't commit to -- I would love to see them used tho!
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Lovely set by Kit <3
The ghost of a witch who used dark magic.. No one really knows how she died but she seems to have passed within the very early part of this century: she claims to be a UCPB but only goes by a first name (should be a common one). Some people suspect she's lying but no one knows for certain (OOC: she is). She tells a vicious, maybe even graphic story about how a mudblood werewolf murdered her (with the emphasis that she never got the justice she deserved) for any sympathetic soul that will lend an ear -- given her funeral garb, it's impossible to dispute her story and she will get angry if you try. She doesn't like other ghosts! What are her real goals though? Does her former practice in the dark arts have anything to do with them? No clue but she is very shady (and probably puts on an innocent act for any suspicious characters, as to avoid the Spirit Division).
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A poltergeist that has set up residency in Hogsmeade somewhere (has to be where there are semi-regular to regular constable patrols), but only comes out at night. They (though most people call them "she" due to their appearance) like to cause mischief and mayhem for the local constables (and occasionally the members of the law enforcement department for the ministry whenever such employees cross their path) among the usual poltergeist shenanigans. There have been several times where they were forced to settle down for a short while, but they have always come back as, unfortunately, you can't get rid of a poltergeist -- a fact that this one reminds the constables (and probably the Spirit Division employees who come to deal with them). They've only picked to bother Hogsmeade since '79. Why? Hogsmeade wished it knew.