Show me again the power of the darkness, and I'll let nothing stand in our way. Show me, Grandfather, and I will finish what you started.
~ Kylo Ren promising to finish Darth Vader's mission to destroy the Jedi thus regarding Vader as his muse.

Muses are characters who inspires others. Normally seen as positive, Muses can easily become negative if twisted in a manner similar to an Evil Genie. Often appearing to individuals or groups, a Muse inspires often them via horrific events of circumstance.

A good example of a villainous Muse is someone who performs grisly misdeeds which another character take as inspiration for their work, whether they become Copycats or something else entirely (such as horror writers gaining inspiration from demons who show them grotesqueries which they use in their work).

Often villainous Muses will see their misdeeds as a type of art and share their "gifts" with those unfortunate enough to be around them. Usually they are feared by everyone around them due to idolizing things traditionally seen as taboo in society, though some exceptionally twisted or desperate individuals may willingly call upon such a Muse when in need of inspiration (as seen in the quote above).