The Runic Golem is a quest in The Golems of Amgarrak DLC. You have found a Runic Golem which you'll have to activate if you wish to increase your chances of survival within Amgarrak Thaig.
Acquisition
Approach the inactive Runic Golem in one of the side-chambers in the Deep Roads Grotto.
Walkthrough
After interacting with the golem, Jerrik Dace will muse that there must be a control rod nearby. Upon leaving the golem's chamber, the mist will have shifted once again, revealing another chamber with the control rod and a Rune Anvil in it. After battling four shrieks, pick up the control rod, return to the golem and activate it.
Result
The Runic Golem re-activates and becomes an incredibly hardy companion.