Melantho is a servant in Odysseus' household. While he is absent, she proves her disloyalty by sleeping with one of the suitors. Also, when Odysseus appears in the form of a beggar, she disrespects him and picks on him, betraying the ethical imperative of hospitality. She acts as a foil to Eurycleia, Odysseus' old nursemaid who is loyal and the first one to recognize her master because she remembers him and longs for his return. The two women are both servants, in similar social positions, but differ by one crucial trait: loyalty. So, a foil is a literary character who is in a parallel position with another character, emphasizing a certain quality in a more distinctive way. Foil is not exactly an antagonist, because he/she doesn't have to act against the "positive" character. They are usually similar in all respects but one - and that one is crucial.
