Rockhound (CR 2)

Small Magical Beast
Alignment: Always Lawful Evil
Initiative: -1 (-1 Dex); Senses: darkvision 120 ft., low-light vision, scent, Listen +2, and Spot +2

AC: 16 (-1 Dex, +1 size, +6 natural), touch 10, flat-footed 16
Hit Dice: 3d10 (25 hp)
Fort +6, Ref +2, Will +0
Speed: 30 ft., burrow 5 ft.
Space: 5 ft./5 ft.
Base Attack +3; Grapple +1
Attack: bite +6 melee (1d4 + 3)
Special Attacks/Actions: final frenzy
Abilities: Str 14, Dex 8, Con 16, Int 6, Wis 10, Cha 10
Special Qualities: Immune to paralysis, phantasms, poison
Feats: Improved Sunder, Power Attack, Track
Skills: Listen +2, Spot +2, and Survival +2
Advancement: 4-6 HD (Small); 7-9 HD (Medium)
Climate/Terrain: Any underground
Organization: Solitary or with master (duergar), understands Duergar
Treasure/Possessions: None

Source: Dragon #357

Adamantine jaws (Ex): Rockhounds have a natural ability to ignore hardness of less than 10 when sundering weapons or attacking objects and creatures.

Final Frenzy (Ex): Rockhounds always fight to their last breath. If an attack reduces a rockhound to negative hit points without killing it, the rockhound can, as a free action, make one last attack with a +4 bonus on its attack roll. Regardless of whether or not it succeeds with this attack the rockhound looses consciousness immediately afterward.

Skills:Rockhounds have a +4 bonus on Survival checks when using scent to track.