what was the role of the hunchback previously mentioned, in this battle?
A  small force led by Leonidas blocked the only road by which the massive Persian army could pass. A local resident named Ephialtes betrayed the Greeks by revealing a small path used by shepherds.
Battle of Thermopylae
After the second day, a local resident named Ephialtes betrayed the Greeks by revealing a small path used by shepherds. 
who played the hunchback in the movie 300 Ephialtes who composed the soundtrack for it? Tyler Bates any particular song which he composed on it? Remember Us and Returns a King who is the main character in the movie? Leonidas I is he based on a real-life character? Yes who? King Leonidas I what was the battle portrayed in the movie which he was a part of? Battle of Thermopylae when did this battle take place? in August or September 480 BC
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Battle of Thermopylae [SEP] Introduction
The vastly outnumbered Greeks held off the Persians for seven days (including three of battle) before the rear-guard was annihilated in one of history's most famous last stands. During two full days of battle, the small force led by Leonidas blocked the only road by which the massive Persian army could pass. After the second day, a local resident named Ephialtes betrayed the Greeks by revealing a small path used by shepherds. It led the Persians behind the Greek lines. Leonidas, aware that his force was being outflanked, dismissed the bulk of the Greek army and remained to guard their retreat with 300 Spartans and 700 Thespians, fighting to the death.