Ossuary Guardian  

These are down in the bottom of the Barrows at the rear of the room where the Celtic sepulchre warriors are. An occasional spawn can be found in the room with the Celtic liches.

The two junk loot items that these guys drop are magical soul anchors & essence of the fervent defender.

The magical soul anchors stack up to 20 in quantity. Selling one anchor to a merchant nets a whopping 5 silver. Selling a stack of 20 nets you 1 gold. A stack of 20 can be salvaged into 1 mithril metal bar which can be trinketed & sold for 99 silver & 36 copper. So best bet is to either sell them outright or fill your pack with more valuable goodies from the deep part of the Barrows!