The Ethereal Mist Earring is an ultra-rare drop from any coterie in Maiden's Eye.
I have made 12 AAs so far, killing only the 8 coteries, across 6 days. They give slighly less than 2% AA per kill, so you can guess how many coteries I have killed...
...and I am still there, without my earring.
Do not attempt to camp this earring! The drop rate is absolutely disgusting. Oh, it does drop; I got two of them in 3 AAs about six months ago, and the previous post proves it still drops. However, if you prize your sanity at all, stay away from those damned vampyres!