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The Ursa is the main antagonist in the 2013 movie After Earth.
The Ursa(s) is/are the alien species that inhabits Nova Prime. The Ursa is used to build tension in the movie, show Kitai's ranger potential, tie in with the theme of the story, and it also creates the climax of the movie. One of he Ursa(s) was taken aboard the ship on the way to Cypher's last voyage to train rangers.This Ursa escaped when the ship crashed.
Ursas are blind and navigate with their senses of smell and hearing, and they hunt prey by smelling for specific hormones one secretes when one feels threatened; they literally smell one's fear.
Role in the movie
When Kitai was little,the Ursa attacked his and his sister,Senshi took to safety where it will not smell his fear. As a result of the attack,the Ursa killed Senshi while Kitai was watching. After the crash, Kitai was sent to receive the beacon (Cypher was unable because his legs were broken but was able to guide Kitai through his way to the beacon). But when Kitai reached the beacon which was near a volcano, he tried to activate it, but there was an interference so Kitai climbed all the way to the top of the volcano but an Ursa had tracked him there. It turns out that the Ursa was the Ursa that escaped the crash, revealing it had survived and hunted Kitai to the top of the side of the volcano.
The two battled each other in an epic final battle, but the Ursa gained the upper hand and wounded Kitai. Just when it seemed that Kitai was about to give up, he remembered what his father had taught him, how to not give up and to always stay on your feet. It gave Kitai the courage and strength to stand back up and kill the Ursa.