Mu Necklace

Cannot be auctioned, traded, or bazaared, but can be delivered to a character on the same account.
Can be obtained as a random reward from the Gobbie Mystery Box Special Dial and similar sources.

Mu (uppercase Μ, lowercase μ; Greek: Μι or Μυ [mi]) is the 12th letter of the Greek alphabet. In the system of Greek numerals it has a value of 40. Mu was derived from the Egyptian hieroglyphic symbol for water. Letters that arose from Mu include the Roman M.