The term “poisoned chalice” is applied to a thing or situation which appears to be good when it is received or experienced by someone, but then becomes or is found to be bad.
The idea was referred to by Benedict of Nursia in one of his exorcisms, found on the Saint Benedict Medal:
Vade retro Satana! Nunquam suade mihi vana!
Sunt mala quae libas. Ipse venena bibas!
Which translates to: “Begone Satan! Never tempt me with your vanities! What you offer me is evil. Drink the poison yourself!”
William Shakespeare uses the expression in Act I Scene VII of Macbeth. It occurs in the opening soliloquy of the scene when Macbeth is considering the ramifications of the murder he is plotting:
“But in these cases
We still have judgment here; that we but teach
Bloody instructions, which, being taught, return
To plague the inventor: this even-handed justice
Commends the ingredients of our poison’d chalice
To our own lips.”