Throughout Act 2 of Baldur's Gate 3, you've probably heard the name Balthazar quite a bit by the time you reach the Gauntlet of Shar. You've probably even been into his study at Moonrise Towers to get a Moon Lantern so you can safely travel the Shadow Cursed Lands. You might have even met him already if you're trying to find Ketheric Thorm's Relic.