The third dark lord

[Fingolfin of the Noldor]

I don't think there actually needed to be. According to Tolkien's letters Sauron was really the last real "incarnation of evil." That is not to say there would be "dark lords" there would, I believe Tolkien also provided for this but simply not of the same sort. The only real time after the destruction of the Ring when a "dark lord" of the same type would become the cheif antagonist, I believe, would be the return of Melkor after, as described in various writings in Morgoth's Ring, after that power he had dispersed through Arda began to pool and acculmulate to such an extant that he could remanifest himself within Ea. Sadly though after the rejection of the second prophecy of mandos Tolkien went into very little detail as to what exactly the final battle would entail and involve. [img]smilies/frown.gif[/img]