Originally a water-dwelling beast from Serbian folklore, the Bukavac was drawn to the Great Plains when the Thunderbird's first tempest cracked the earth, revealing vast networks of underground chambers filled with ancient power. Transformed by centuries of exposure to the minerals and energy within these sacred spaces, it evolved into a burrowing guardian that forms symbiotic bonds with those who prove their worthiness through trials of physical endurance and respect for the land.

The Burrowing Bukavac possesses six muscular limbs ending in diamond-hard claws capable of carving through solid rock, while specialized sensory organs along its spine can detect the faintest vibrations of hidden chambers and artifacts buried deep within the earth. Its horns serve as conduits for the Thunderbird's earthbound energy, occasionally emitting crackling arcs of electricity that illuminate unexplored passages and activate dormant petroglyphs. Though fiercely territorial around sacred sites, it forms unbreakable bonds with those who demonstrate both physical prowess and reverence for the land's ancient secrets.

The Burrowing Bukavac guides worthy members of the Earthbound Guardians through treacherous underground passages to sacred chambers containing artifacts imbued with the Thunderbird's earth-bound power, while fiercely protecting these sites from those who would exploit rather than honor their wisdom.