I believe you need to turn in all mage amulets for unlock, but is the rainbow Mage Amulet one of the ones required?

This is what the guide had:

The Mage Complete Mage Quests by turning in one of each type of Mage Amulet consecutively

The rainbow one is not on the list.

Hope this helps and good luck!

I was looking at a different guide, can see the other one now with the mage amulets listed. Thank you for the response,

You're welcome. I went to a couple of different places before I found the answer I was satisfied with. I totally understand some being confusing or not getting the exact info you're looking for.

I would tell you to have fun battling the mage, but there is no fun to be had when battling him! ;)