Could Durins Bane have become more powerful over time

[Morthoron]

Originally Posted by Boromir88

I think that Letter 131 quote is about Sauron's power to corrupt and dominate the minds and wills of others was enhanced, but the "power" Morthoron is talking about is Sauron's (and I have no better way to describe it) physical and spiritual power diminished....

So, I would argue, the power the Ring "enhanced" was Sauron's attempt of empire-building in dominating "minds and wills" of others, but this did diminish his inherent power. What Tolkien refers to in Letter 200 has the "line between the indestructible mind and being and the realization if its imagination". The link between what one could call "will power" and "real (or maybe physical) power" weakened by Sauron's creation of the Ring.

Thank you, Boro. That is precisely what I was getting at when I stated:

"Actually, his only true power was the domination of lesser beings, in a netherworldly ability to corrupt, and the Rings allowed him to do that with greater efficacy. However, Sauron as a Maia exhibits the same personal decline that his predecessor Morgoth did; but whereas Morgoth dissipated his power into Middle-earth itself, Sauron placed his potency in the One Ring."

Morgoth corrupted the very earth, whereas Sauron corrupted minds. For that, Sauron was much more of a modernist in method than the god of chaos, Morgoth.