Penumbra was a sublabel of Umbra specialized in EP length soundscapes typically around 20 to 25 minutes in length. All were released as 3" CDs in very limited quantities and sold out fast. Most of the music released in this label were created by artists also releasing in Umbra label such like Oöphoi, Klaus Wiese, Tau Ceti, L.E.M., Netherworld, Seren Ffordd, Perceptual Defence and Sostrah Tinnitus among others with both solo and collaborative music.
These EPs were later compiled as full lenght albums under "Penumbra EP Collection" title. A total of 10 volumes were released collecting music of 3x EP per each CD. Those albums were also limited editions and were quickly sold out.