This achievement is called "Stone Cold" to get it you must defeat the Rock Wraith on your expedition into the Deep Roads.
After speaking to a fade rock spirit follow the path and the Rock Wraith will appear. When fighting the Rock Wraith, after a certain point it will curl up into a ball and begin to glow at this point move to a corner behind a column and you will be protected from the damage, after this happens it will summon Profane's. Take out the Profane's first then resume attacking the Rock Wraith while its down. Then it will soon rise, then just rinse and repeat until its defeated, keeping your health up as necessary. Once you have defeated it the achievement will pop.