The forest covering southern Ios, stretching from the Dipindre valley to the coast. Koilos is dense and largely unexplored — the stone dolls never worked there (they were designed for agriculture and construction, not forestry), and Ios never developed a timber industry.
The forest is rumored to hold ruins from before the current settlement, structures that predate even Todakres. Whether these are remnants of an earlier civilization or something else entirely, no one knows. Few Ios citizens venture into Koilos, and those who do don't always return.