He is a servant of Eld Stagger and frequently did battle with Momma Kodi in an attempt to steal her land.
"Can anyone tell me how the wolf beat up an enemy whose skin he couldn’t pierce?”
When Brennen arrived to The Green Ravine River Valley, Anvilback was the first opponent he faced. The badger was possessed of a hide that was incredibly tough, possibly enhanced by his king's magical powers. Brennen's teeth could not inflict any damage on it. He could, however, apply enough pressure to break the bones underneath. He used his jaws to snap one of Anvilback's legs, causing the badger to retreat.
Anvilback is mentioned during one of Kelly Clegg's first conversations with the forest boy. The boy informs her that he had seen Anvilback taking Emma Lee Hagen out of the cursed part of the woods, across the river bed and into Kodi's land. The badger seemed terrified at the very thought of the bear.
Anvilback only appears in person during the battle in the river in 2015. The combination of the rainstorm and the curse of the forest cause the river bed to transform instantly into its flooded, raging form. The badger appears alongside Laylah Flaherty and draws Kodi into the river to fight. The boy and Kelly fail to understand why Anvilback is no longer afraid of the bear.
The badger's temerity surprises even Kodi, with Anvilback leaping up at her and getting in close to slash at her with his claws. She grabs hold of him, but his skin is so loose he can turn freely and keep hitting her.
The witnesses to the battle soon discover the reason for the badger's bravery: Anvilback's companion, Drag-Belly, is waiting in ambush. The two beasts initially get the upper hand against Kodi; Drag-Belly bites her head and pulls her into a death roll, while Anvilback attacks her legs and keeps her off-balance to prevent her from breaking free.
When Garrett interrupts the fight by howling, a ploy to fool the two monsters into thinking King Firehide has arrived, Drag-Belly is the one to go investigate the noise. Anvilback tries to continue the fight with Kodi, but she bites his ear, which puts her in control of his movements. She forces his head under the water and uses her weight to keep it there, bypassing his invincible hide as her husband had done.
Kodi drowns Anvilback in the river while Drag-Belly is occupied dealing with Kelly and Garrett.
Later, Stagger intends to use the Leviathan to revive Anvilback, but he never gets the chance.