I can also have mortal beings ascend to Godhood. If an individual has done something exceptional that causes a large enough quantity of people to view them as a god, then they will over time become a god. Usually, this process happens after the person in question is long dead, but it doesn't necessarily have to.

Again, time to reccomend those Requiem for Homo Sapience books that I mentioned earlier. This time, along with its predecessor, Neverness.

And, of course, that's also in the Dune, the Malazans you wrote about, and many more.

Cheers :)