Thinking about it a 40k version of the calssical evil dragon myth would be a deamon prince like creature. Because dragons can talk and reason and manipulate and have fundmental flaws leading to their death of greed and envy.
Being a 40k dragon I can see the hoard being the corpses and armour of all that tried to slay it and failed. A mountian of Adamantium corpses, whole chapters piled atop one another. Kyn bodies, flesh and iron. Both tomb and treasure hall