Final answer:
Claudius' reference to the 'primal eldest curse' is an allusion to the story of Cain and Abel from the Bible, representing the gravity and eternal consequences of his crime.
Step-by-step explanation:
Claudius' reference to the 'primal eldest curse' associated with his crime is an allusion to the story of Cain and Abel from the Bible. In the story, Cain commits the first murder by killing his brother Abel, and is cursed by God as a result.
This allusion suggests that Claudius is acknowledging the gravity of his crime and the eternal consequences it carries, much like the curse carried by Cain in the biblical story.