Copy protection

Copy Protection is used in three of the King's Quests (III, IV, VI).

Copy Protection in King's Quest III
The pages of the spell book which are needed to eventually escape from Manannan are the copy protection.

Copy Protection in King's Quest IV
King's Quest IV uses excerpts from a group of paragraphs as copy protection. (Such as Page 1, 3rd paragraph, 1st word.)

Copy Protection in King's Quest VI
The Ancient Ones alphabet from the Guidbook to the Land of the Green Isles is used as the copy protection. You must have the alphabet to ascend the Cliff of Logic succesfully.