Chalkhos's binary twin is a barren world that's always seemed like a better terraforming prospect that it is. Its temperatures are quite tolerable for sapient life, and its gravity is suitable for retaining a thick atmosphere. Its location, close to Chalkhos, makes for a tempting investment--two garden worlds so close together would benefit from mutual trade and, if nothing else, tourism due to their near-unique status. However, Selvos has minimal water. Early attempts at creating a hydrosphere met with slow progress that only Chalkhos's asari could love.
The deaths of the colonists on Selvos and Chalkhos have dashed any hope for terraforming in the near future. Selvos is now a wasteland of punctured domed habitats and its orbital stations are slag. The Reapers have moved on.