From the Warlock manual (C64).

WARLOCK consists of 20 different levels, with each level increasing in difficulty. You goal is to re-capture the stolen "Karna", the precious jewel of the Underworld. Your only defenses are your vitality, power, and objects you find along the way. Your mission is to collect eight magical objects that are hidden among the 20 screens. As you collect the objects, they will appear in the upper right portion of the screen. Only after you have collected all eight objects, can you attempt to re-capture the Karna.
Its thief is know only as evil HE.