Huh. I don't think I know of any villainous bards in any media I've watched lately. Closest would be Dethklok from Metalocalypse, because their music causes carnage around them, but they kinda save the world from being destroyed by Salacia. There's also Drosselmyer from Princess Tutu, who is obsessed with controlling reality through storytelling. Maybe look at the examples on this tvtrope's page for some inspiration:
>https://tvtropes.org/pmwiki/pmwiki.php/Main/MusicalAssassin
In any case, the Bard keeps and tells stories. Usually, to sing praise of how the heroes have helped the world. But what if this Bard Villain believes that these stories have become a cage in which the powerful gets to control everyone? And then he forms a cabal of performers to spread rumors, to create blackmail networks, and to assassinate anyone who tells a subversive story. And with magic involve, maybe this Villain and his lieutenants can use "Modify Memory" to control their audiences. I can already see how fucked things can get with a villain who can change how people are able to remember things.
Some other ideas floating about in my head:
>Villain's name is a Half-Elf named Maestro Callis Refrayne
>a magical revolver that fires harsh noise at enemies and causes them to fall under the effects of the "Confusion" spell
>Has "Symphony of Ruin", a legendary performance action that destabilizes any political figure's reputation in real time.
>A unique ability where Maestro Refrayne can physically change the environment if he can manipulate enough people to believe it to change. Essentially Sigil, but on a more localized level
>Cabal Name: Chorus Obscurus