"A dark mysterious emblem found in Dol Guldur. This can be exchanged in Emyn Lum."
Quoted from: Aruen
This is a barter item which trades in for boots that always have +30 Radiance on it. To equip the boots, you must be level 65.
This item drops from "Durchest", the first boss in the "Barad Guldur" raid instance. In my opinion, you need to be level 65 and have 115+ Radiance to venture into Barad Guldur.