Thoranayudham (The Battle at the Entrance) is a Kathakali play (Aattakatha) authored by Kottarakara Thampuran in Malayalam. Based on the Ramayana, it narrates the events surrounding Hanuman's journey to Lanka in order to locate Seetha and convey to her the message from Rama.
References
Thoranayudham Wikipedia(Text) CC BY-SA