I found it while fishing on the Dragon Isles. In it was 图样：虚空法袍

Item is believed to have been removed from the game before making it to live. Only included the Pattern mentioned in the other comments.

小知识

屏幕截图

视频

瓶中的陈年配方

物品等级：70
拾取后绑定

"看起来已经在艾泽拉斯各地漂了一段时间。现在，来自遥远过去的配方来到了你面前。"
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