 Although the Ephors have denied him permission to mobilize Sparta 's army , Leonidas gathers three hundred of his best soldiers in the guise of his personal bodyguard ; they are joined along the way by Arcadians . At Thermopylae , they construct the wall made up of stones and slain Persian scouts as mortar , angering the Persian Emissary . Stelios , an elite Spartan soldier , orders him to go back to the Persian lines and warn Xerxes after cutting off his whipping arm . Meanwhile , Leonidas encounters Ephialtes , a deformed Spartan whose parents fled Sparta to spare him certain infanticide . Ephialtes asks to redeem his father 's name by joining Leonidas ' army , warning him of a secret ( goat ) path the Persians could use to outflank and surround the Spartans . Though sympathetic , Leonidas rejects him since his deformity physically prevents him from holding his shield high enough ; potentially compromising the phalanx formation , and Ephialtes is enraged . 
