Key 0028

It used to open a door in King Tibianus' Rain Castle's magic in Thais where Trimegis is, here. It is unknown if copies of this key still exist. Furthermore, any existing copy might not be functional anymore, since similar keys are said to have been disabled with the Summer Update 2007.

It's also not known for sure what material it was made of, however, it's assumed to be Silver since most other keys of Thais city doors were also made of this material.