The Demogorgon statue is in the Kuo-toa lair,.. just explore and you'll find it [img]smile.gif[/img]
Only thing you'll have to do at that point is give the statue an animal sacrifice. You can do this by either summoning a creature and directing it to the altar or lure a Kuo-toa onto the base of the statue.
Have fun
It's a really nice statue you see, if you give it a sacrifice, it'll give a few things back [img]tongue.gif[/img]