Serpent Riders' Icons are found throughout Heretic and Hexen levels. They are often found on the walls or on altars and sometimes also on stained-glass windows.
In Heretic, D'Sparil icons are found throughout Parthoris world. They are D'Sparil or Serpent Riders images found on walls or on stained-glass windows.
In Hexen, Korax icons can be found throughout Cronos.