Doom metal overlaps a bit with some occult / retro bands for which I made a thread some time ago.
Candlemass basically invented the modern conception of that genre, and Avatarium were born as a side project of Candlemass' bassist and leader. If you don't know them, absolutely check their debut album and especially the song Moonhorse.
If you want some STRONG Sabbath vibes, check also Uncle Acid and the Deadbeats, the song Death's Door should give an idea of their sound.
If you like Avatarium and the retro sound of Uncle Acid, you might want as well to check Blood Ceremony, the bastard child of Jethro Thull and Black Sabbath, even though we might be floating here towards more the hard rock side of things than the plodding and menacing pace of doom metal.