In Greek mythology, the muses are the goddesses or spirits who inspire the creation of literature and the arts.
Is there a mythology that includes an “anti-muse”? A god, goddess, spirit, whose main function is the opposite–to discourage, repress, drain, destroy inspiration and creativity?
If Greek or Roman myth includes such a figure, I’ve missed it. What about Hindu, Nordic, Celtic myth? Or other?
I think Loki might fit the description somewhat, as he frequently tried to make sure the endeavours of others would fail just for the Hel of it.
There must be. I think Loki (and other malicious trickster types) would fall under the more general banner of “being a prick” though. Then again, an anti-muse would be the god of a lack of arts. That doesn’t really make much sense when you think about it that way.
Of course you could argue that some muses were opposites of each other (e.g. Melpomene for tragedy and Thalia for comedy).
That would be amusing. 
I think that would be the god of bureaucracy and red tape.
I think it’s safe to say “no.” There are plenty of mythological tricksters, who mess with the world order, and classes of beings that are ranged against the gods in general, such as demons, but I sincerely doubt if there’s a deity of writer’s block. If there were, it would be someone like the Muses or Ganesh withholding their favors rather than a specific anti-Muse.
Not classical mythology, but you’ve got the Person from Porlock as an iconic figure of this.
Calling CalMeacham!
Eris is probably the closest major figure in classical mythology, but she’s not an exact match.
As noted in another thread, there’s Lyssa, goddess of rage, anger, and rabies.
As far as I know, there was no Loki cult or a general understanding that he had any part in the lives of men (which Tor, Odin, Freya, etc had). Malicious types were rather trolls and such, and various oknytt – goblins, elfs etc – could play tricks on you, give you bad luck, and so forth, if you gave them reason to, so to speak. But I have never read or heard that anybody blamed Loki for anything. He was very popular as a character in tales etc, but not really part of the Scandinavian belief system.
As to the OP, I’m no expert, but I’ve read a lot of mythology through the years, and I can’t recall the type of being you’re asking for.
Death
If you think about it, the presence of a muse in those pantheons explains the absence of an anti-muse. If you need someone to inspire you, then it’s suggesting that a lack of ideas is the natural state of man.
Murcia was the Roman goddess of sloth and inactivity. Koalemus was the Greek god of stupidity or foolishness.
Well I don’t recall saying he was…