You just have to keep fighting them, at the end of the battle there's a chance one will stand up and admit to being the gold-plated golem. There's absolutely no way to tell beforehand, just keep fighting them and it will happen.
in elemental but u have to complete everything and every quest
You can't but you can make one @ dragon quest monsters.com
You first need to find Nulgath larvae and you have to accept the quest and you have to defeat the Mana Golem and complete the quest then you get the hex blade of Nulgath
It should be in the shrine of Palaish Isle.
gittinghampalace
U have to fight him in warlic's quest(dragon egg)
oaklore dragon defend oaklore quest
nythrea's first quest you'll find it on that one
you first have to find nulgath larvae and you accept the quest then you join elemental and you defeat mana golem several times. after completing the quest you tum in and you get hex blade of nulgath.
In Dragonfable you can find the mummy dragon in a quest called Dynasty Tomb in the Sandsea from Zhoom.
Go to below link and go to non-member quest and find dragon slayer quest. It is a good guide with screenshots.
You find them in high level 'volcano' grottoes.