Needs review
Source: Races of Stone

Description: You have studied the techniques of fighting underground, and you can protect yourself from the dangers of multiple attackers whenever you can put your back to a solid wall.

Prerequisites: Shield Proficiency, Tunnel Fighting

If you have a ready shield with which you are proficient and one side of your space is entirely in contact with a solid wall, you cannot be flanked.

Special

A fighter may select Stoneback as one of his fighter bonus feats.