Derek the Bard defeats an evil time-traveling Black Lantern vampire on Christmas Eve. By casting Dragon Slave.
And when the vampire returns and traps him in a void-dimension in episode 18, the Bard uses the Full Body Bind Curse. "Until the next time you come back, this is Derek the Bard. Be seeing you, bitch!"
Winning the duel against immortal book-thief Dorian Gray in episode 19.
"Just so we're clear, I'm not going to kill you. I want you to take a message back to all your little evil friends out there to please, for the love of God, leave me and this library alone. I didn't sign on to fight the forces of evil, I just signed on to maintain these books. But if you put my back up against a wall you would not BELIEVE how unpleasant I can make your existence. I'm not a fighter, a thief, an adventurer, or a gunslinger. I... am a LIBRARIAN. And if you force me to, I will take all the secrets locked within these stacks and I WILL use them against you! Do we have an understanding, Mister Gray?"