Shroud Flayers are found in the Nomad Highlands region. You can collect Shroud Adhesive by killing a Shroud Flayer. You can make Shroud Flayer seedlings from the collected Shroud Adhesive, and plant those seedlings in Shroud Infused Farm Soil that you craft with the farmer and place within your base area. I highly recommend this as the Shroud Adhesive is useful.