In Norse mythology, Nidhogg ("tearer of corpses") was the monster that ate the roots of the World Tree, Yggdrasil and swore at the eagle living in the tree's branches. Nidhogg also ate corpses.
... of existing "digital rights management" and "copy protection" systems:
Serial copy management system[?] (SCMS)
Macrovision
iTunes
Windows media player[?]
...