Ok so in basic terms, ad hominem is attacking your opponent and not there position. An example would be: You cannot believe my opponent; his hair is untidy and his visage is beyond unprofessional. By saying that the opponent is "untidy and unprofessional", you are attacking his character. Rather than arguing against his position, the attack of the opponent's character is Ad hominem. I hope this helps :-)
Polyneices is being compared to an eagle in this excerpt from Antigone by Sophocles. The chorus leader compares him to a soaring eagle flying high above our land. Somebody else is being compared to an army, but not Polyneices.