Thanks to Shar's Page
Mummy King is located on Nork -3
Find the key to mummy king in Nork -3, it is a random treasure. After you get the key you go to the NE corner of -3 and open the locked set of double doors you find there.
You then kill the Mummy King. Take the Mummy King to be tanned and take the cloak to Wartberg, the man behind the west bank. Drop the cloak and some money, about 3K, type in "war, sell" to get the ammy from him, not trading in the usual way where you just click on the npc and get handed the items.
The amulet is ProStun level 10 and has a random number of charges. The ProStun twigs you buy in Maeling are level 8, and have 4 charges.
Jimmy Whitaker sent in the tip for what to type in order to get the ammy. Thanks Jimmy :)