Compendium One contained an article on The Mark of Chaos that featured 3 Chaos monsters, Ngaaranh Spawn of Chaos, Zygor Snake Arms and Leaping Slomm Two Face, shown below. Slomm and Ngaaranh were later released as part of the c27 Chaos Monsters range. There is an unreleased version of Leaping Slomm that is closer to the illustration, but apparently would not cast, it is extremely rare.
Painter:
Andrew Taylor / Adam Skinner
Released:
1983
Ngaaranh Spawn of Chaos, Leaping Slomm Two-Face & Zygor Snake Arms
Ngaaranh, Spawn of Chaos
Leaping Slomm Two-Face
Zygor Snake-Arms