This one just sort of "starts" on its own when you step into the Lost City map area. Everything goes dark! You have to go back and talk to Drognan. He talks about the Claw Vipers - that you have to find the (get this) Serpent Altar, in the Claw Viper Temple, in the Valley of Snakes. Hmmmmmmmmm.

You run into Night Tigers, Night Slingers, and Fire Towers. Off of the Lost City map area is a VERY small area which is of course the Valley of Snakes. The Claw Viper Temple is only 2 levels, and the second level only has the altar in it. Not only do you finish Quest 3 when you hit the altar, but you also find the Viper Amulet, which is the head of the staff.

Diablo 2 Walkthrough
Walkthrough Master Index