It can be reached, with some effort and no flying, by climbing up the hills near Oneiros. The island in the centre has a collection of Alliance Level 85 NPCs (except for the cats, who are Level 1), several of whom have names odd for their race. They are not hostile to Horde visitors.
According to various sources, these are all the names of Blizzard employees from one particular team.
A twisting arm of the lake extends up into only semi-mapped mountainous territory along the borders of Desolace and Mulgore. The steep hills are littered with night elf ruins, most similar in appearance to those in Desolace.
From Mulgore, Palemane Rock's caverns appear to run partway under the easternmost extent of the lake; from Lake Dumont, after a difficult-to-climb incline out of the water, there is a fairly gentle rise which leads straight into Tauren territory near Stonebull Lake.
Videos EditCataclysm Beta - The Island of Misfit Blizzard Employees!(01:49)
Feralas Lake Dumont (before flight) - WoW patch 4.0.3(05:19)