This serpentine dragon has skin the color of deep volcanic rock, enormous claws, and jagged, stonelike horns and scales.
CR 3; Size Tiny; Hit Dice 4d12
The claws of an underworld dragon are made of adamantine, and have the qualities of a weapon made from that material.
As a full-round action, a great wyrm underworld dragon can burrow through the ground up to twice its burrow speed. At the end of that movement, if the underworld dragon has use of its breath weapon, it can emerge from the ground spouting lava in a 30-foot-radius burst, dealing damage as the breath weapon.
A very young and older underworld dragon can see perfectly in smoky conditions (such as those created by pyrotechnics).
An adult underworld dragon gains a 10-foot bonus to its burrow speed. When the underworld dragon becomes old and every two age categories thereafter, its burrow speed increases by an additional 10 feet.