Who is The Great Om from Small Gods: A Novel of Discworld and what is their importance?

At the start of the novel, the Great Om appears as an impotent version of a wrathful god. Over the course of the novel, however, the once mighty god is schooled in humility and weakness. When Om sees evidence of the horrors committed in his name, he comes to understand that he is just as accountable to man, as man is accountable to him. By the end of the novel, Om formes a partnership with Brutha, in which, he agrees to be governed by the same rules that govern men.