The term 'CASTOR BEAN POISON' is composed of five crossword solutions: ricin (5 letters), oilseed (7 letters), Idas (4 letters), HAT (3 letters), and Leda (4 letters). Ricin is a toxic protein found in castor beans, which is used as a biological weapon. Oilseed is a type of seed that is used to produce oil, such as castor beans. Idas was a prince of Thebes in Greek mythology who was killed by a castor bean. HAT is a reference to the Greek myth of Idas, in which he was killed by a HAT thrown by the goddess Athena. Leda was a queen of Sparta in Greek mythology who was seduced by Zeus in the form of a swan, and she gave birth to two sets of twins, one of which were Castor and Pollux.