Phantom Zant is the Mini-Boss of the eighth Dungeon in Twilight Princess, the Palace of Twilight. Defeating him will reward Link with the access to the Sol, which must be taken from the Zant's Hand. He is fought twice within the Palace of Twilight, and there is one guarding each Sol.
Phantom Zant will start the battle by summoning a Ball of Twilight, which will spawn groups of Shadow Keese, Shadow Beasts, and Twilit Babas. After summoning the ball, Phantom Zant will warp around the room. After defeating all the monsters summoned by Phantom Zant, he will teleport around the room, and stop to summon enemies. This is the best time to attack him, as he will be distracted. Attacking him will also cause him to stop making his ball. He will repeat this process throughout the entire battle. After doing enough damage, he will be defeated, and access to the Sol will be granted.