every race in wow was created either by the titans or an animal agent, with few exceptions.
all animal races, such as murlocs, tauren, quillboar, all come from animal ancients, which are basically "gods" of that animal. one example is that quillboars came from Agamggan, a giant pig ancient. note: worgens are NOT an animal race, they are a form which originates from a druidic wolf form. worgen itself isn't really a race, rather a form. like gilneans, despite being worgens gilneans are still humans, etc.
the rest of the races that don't come from animal ancients were made by the titans. these races are all the giants, vrykul, mechagnomes, mogu, and earthen. when afflicted with the curse of flesh, these stone/metal skinned races became fleshy. giants would get flesh, vrykul would get flesh and later some became humans, mechagnomes would become gnomes, earthen would become dwarves, and the mogu would get flesh too.
lastly, for the exceptions. some races where not made by titans or animal ancients.
orcs and ogres arn't from azeroth, they instead came through the dark portal from another planet, Draenor. their true origins are unknown, but it is known that ogres came from the Gronn.
goblin origins are unknown, but it is speculated they where actually created by the old gods, like faceless ones. this is because goblins are inherently "evil" and one faceless one remarks "I remember when your race was created" to a goblin
trolls origins are unknown, but they where one of the first races on azeroth, before even the titans came. the dark trolls around the well of eternity would eventually evolve into night elves.
