Technically part of the Vesayen Isles, the Shadow Governess' Isle isn't reachable by normal means. This isle was part of the Should the Stars Fall Live Event when the Shadow Governess held one part of the Silver Key that would open the way to the Shard of the Herald.
"It's secretly named after Savo, a volcanic cinder cone off the northwest coast of Guadalcanal that several major sea battles were fought around in WWII." [1]