Why Sauron wants the Ring?

[Sarumian]

Originally Posted by Drognan

Do we know what powers Ring provides? It's allready known that turns person invisible and greedy, it can control other rings, what else?

I suppose it is able to subdue others' wills and amplify spells focusing them precisely. As such an amplifier it is possibly more powerful than the staffs of Istari. The Ring's ability to bend others to his Master's will is enormous.

I agree with what was already said but would like to add that Sauron probably suffers the loss of the Ring almost in a physical way. He is incomplete, inconsistent without it. It is like feeling ill. He can't fully recover without it. In this respect he feels similar to Gollum, Saruman or Denethor who all became the Ring's victims.