Under Neith is a single player map for Doom, requiring a limit removing source port. The map was created by Owen "Sarge Baldy" Lloyd and features textures by Nick "NiGHTMARE" Baker as well as the level's author. It was released on 24 January 2005, and is the sequel to Neith.
As the title suggests, the map takes place under the surface of the imaginary moon Neith, and as a result it is darker atmospherically than its prequel. Though the map follows Neith in making use of the berserk pack, it does so to a somewhat lesser extent. The map structure is also far less linear. Though some found this made the map too mazy, it was nevertheless well-received, winning "wad of the week" honors in Newstuff  as well as being the first map to receive Darren "Doom Dude" Finch's Level of the Day accolade.