Giant Subterranean Lizards are a species of huge lizards with pale yellow or white skin which are found only in large underground areas. They are predators who hunt in large cave or tunnel systems. Though they are large, they are able to slow their metabolisms such that they can go without food or water for months at a time if necessary.

Giant subterranean lizards are very quiet and normally gain surprise on 1-3 on 1d6 because of this feature. Though they are not particularly smart, they are able to remember the tunnels in which they commonly hunt in great detail (and in three dimensions) and will always take the most effective route in pursuit of their prey. Worse, they often hunt in groups, and will cunningly choose to herd fleeing prey into dead ends or into crossings where the lizards may fall upon them from several directions at once.