Who gives you the Umar Hills quest. And where can he/she be found.
I want Mazzy in my party.

Little boy, south of the Copper Coronet (Docks) gets you started. Talk to the Mayor in the hills, check out the other houses. Find the new area on the map. Walk.

You want the cute halfling Mazzy? Well, you'll find her in the "dungeon-like-temple" trapped in a room whilst doing the umar hills quest.You'll be directed to this temple by a female werewolf. Just beware of those arrow shooting orcs along the corners of the room.

otherwise talk to the mage in the concil building in the government district and agree to hunt down valygar.
in my second (present) game the little boy didn't come and talk to me.

Good gaming

You don't need to wait for the boy to find you. He's standing next to the pidgeon-dropping covered statue in the Government District, telling the world at large that he has an offer for it.