Thraxx is a giant insect that lives inside the head of the even larger insect skeleton in the Bugmuck. It is the first official boss of the game, and notably appears on the game's boxart.
While searching for ingredients in the Bugmuck, Strong Heart, of Fire Eyes' Village, unwittingly came across Thraxx, who captured him and trapped him in silk. When the Hero went looking for Strong Heart after learning from Fire Eyes that he had gone missing in the Bugmuck, he found Thraxx inside the insect skeleton. After an intense battle, Thraxx was destroyed, and Strong Heart was rescued.
Thraxx may appear daunting at first glance, but only the heart needs to be destroyed in order to defeat it. Thraxx casts Acid Rain and can roar, knocking both the hero and the dog back across the area and dealing damage. Maggots also spawn throughout the battle; if there are less than two maggots at any time, more will spawn until there are four. Thraxx's claws will attack the player when they get close, and can be destroyed if the player wishes.
Attacking Thraxx's ribcage will deal minor damage, and more important cause its ribcage to open, allowing the player to get inside and strike Thraxx's heart.
Whenever Thraxx's heart takes damage, it retaliates with its roar attack to knock the player out of its ripcage and dealing 5 pure damage to the character the player is currently controlling. This makes it a solid strategy to attack the heart with the dog (has highest attack value) and instantly changing control to the player, so he takes the damage and is pushed back. Then changing control to the dog again (or using the sniff button), so he remains positioned inside the ribcage (otherwise he returns to the boy).
The heart has a unique defense mechanic; Every time it is hit, its defense lowers. Its defense refreshes if it has not been hit for 10 seconds, however.
If the player has levelled up the Bone Crusher at least once, charged weapon attacks work well to quickly deplete Thraxx's health; use a normal attack to open the ribcage, then charge up a stronger attack once inside.
If the player is low on Petals or close to reaching a level up, the Maggots spawning may be killed to drop them or grant experience to provide healing.
Defeating Thraxx will earn 750 experience, 750 Talons, and the Spider's Claw. The player can then use the Spider Claw to free Strong Heart. The player also receives 10 Wax and Oil. If however either of the two ingredients were at an amount of 90 or higher, the player will receive 300 Talons. If they also kill both the Claws (Thraxx), they receive another 300 Talons. The player can earn a total of 1350 Talons.
Rarely, Thraxx uses Acid Rain on a Maggot. This is mostlikely a bug.