Who is Bokrug from Dagon and Other Macabre Tales and what is their importance?

Bokrug appears in the story, The Doom that Came to Sarnath. He is the water lizard god, who is worshipped by the inhabitants of Ib. After Ib is destroyed, Bokrug is taken to Sarnath, where he stays for 1,000 years, after which, he arises from beneath the lake and destroys Sarnath.