Origins
Murloc
After the Old Gods left the world now known as Azeroth, life began to live on its own. The first of this life existed in the sea, as it must be. Even so far away from the Well of Eternity, life began to fill the world. Soon, this simple life began to grow into larger forms, sped by the magic.
The first of the more complex creatures were influenced by Neptulon the Tidehunter. Enraged at his sister's betrayal, he made the waves crash harder upon the earth. This killed his fish servants, however, who helped to destroy the earth. He puzzled over this for many centuries.
Looking to the land, Neptulon found that the Well of Eternity, which imprisoned his master, granted life even in his dark seas. The fish that now served him were dependent upon this energy. He forced a mutation that caused some fish to go out of the seas at low tide to explore with their newly altered fins.
Many of these fish found an unexpected problem. Though they could crawl on land, they were unable to avoid being eaten. Birds and other small creatures ate all of them as they reached the shore. Finally, Neptulon decided to force a small group to continue developing.
Limbs soon began to grow in earnest on these creatures. The day of the final test came, and much faster than they had been born, they were wiped out. In his fury, Neptulon struck the continent with harsh waves. This brought the attention of the Sea Giants, which only slowed his progress. An idea came to him then.
His earlier attempts had been with weak fish that preyed upon small aquatic plants and incredibly small creatures. He instead worked on a natural predator that hunted other fish, and put much more power into it. Then, in an act of inspiration, his creations were commanded not to attack the Sea Giants, but to worship them. One day his creatures would return to the sea in a greater form, and would command their lesser brethren.
Some of the creatures, now known as Murlocs, chose to live on land as directed by Neptulon. These changed greatly, but that tale can wait for now.
AN: Short, I know, but that is more or less what I think led to the creation of the Murloc race. Besides, I'm far more interested in the ones that ended up on land, so I cut it short.