Bavadil the Blue is a mischievous creature that uses his illusory magics to his advantage, throwing those that hunt him off of his scent. He is cunning, charismatic, and confusing to face off against. His fighting tactics are questionable, and his speech even more so.
Bavadil is a cheeky fellow. He says what he thinks but will do it in a way so as to not allow the conversational partner to realize he just outright insulted them. He'll talk his way into someone letting him stay in their house, talk people out of their belongings, and talk people into their beds. He's been forced to leave many a town due to the last part.
He doesn't seem to have many goals, he acts impulsively, and he does what he wants to when he wants to.
The right music helps set the tone amazingly. There are really two stages to this encounter - the roleplay and the fight.
During the roleplay, something something cheeky and guard lowering is solid. For hyper charismatic, yet slightly scummy people, I like to use The Troll Shop Theme from Gwent: A Witcher Card Game. It's very disarming, and puts the listener at ease a bit given the slightly goofy nature. Or, hey, if you want to play him as more of an outright scumbag, Snake Soul from Pyre is an amazing option.