Not to be confused with the Goblin Summoner, a much stronger, Hardmode enemy that spawns during the Goblin Invasion.
The Goblin Sorcerer is an enemy that spawns during the Goblin Army event. Approximately one out of every nine goblins will be a Sorcerer (11.11% chance to spawn). The Goblin Sorcerer fires three Chaos Balls in succession that travel through blocks, and it teleports. The Sorcerer cannot fire and won't teleport when taking damage.
Aim for the head as that is where the projectiles are fired from.
The Chaos Balls can be destroyed by hitting them with another projectile or a melee weapon.
The Bestiary entry for the Goblin Sorcerer: "As primitive as they are, some goblins have the potential for manipulating magicked shadow energy through a form of hexing."