Baal, also known as Raiden Shogun, the Electro Archon, and the God of Eternity (just to confuse matters) is the leader of Inazuma and commands an army, led by another new character, Kujou Sara. Baal believes in achieving divine eternity, and to that end, Visions should be harvested and inlaid to the statue of the Thousand-Armed, Hundred-Eyed God. There are a few story spoilers ahead, so avert your gaze now.
Although Baal is a formidable character, there are other characters in Inazuma prepared to help you, including Gorou, the leader of the resistance, as well as new Genshin Impact characters: Ayaka, Yoimiya, and Sayu. You do have a run-in with Baal in the Archon Quest Chapter 2 Act II, our Baal Boss fight guide can help you out with that one.