Originally Posted by
Kriegery
It could be possible that there is a 18th piece.
Not sure if you need Adamantium Headphones for full Adamantium Headphones, could be the same with Amethyst. Not sure what the item could be, though
I believe headphones were required for me to get the adamantium achievement. I edited my previous post at the same time you were replying, so I offered an alternative solution there.