By my beard! Do you know what this is?! It's an ancient tablet that describes how to forge the Bulwark of the Mountain King!
The last one to wear that armor was Aegrim Bronzebeard, my ancestor and thane of the Bronzebeard clan.
Talk to Advisor Belgrum. He'll know more about Aegrim's past, and might be able to shine some light on the legends of his armor.