The Tyrannox Hat is obtained by defeating the Tyrannox in the Forest biome. There is a 20% chance you will obtain it when you die.
"A must have for any true fan of the Tyrannox. This hat is carefully crafted from Tyrannox hides and organs, granting the wearer the ability to summon highly toxic meteors that scale with MAG when attacking barehanded. Consumes 1 Mana."