Complex sentence: When he climbs back down, he exiles Loki from Asgard and then rallies the Asgardians to begin fighting back, to show their enemies why they are known as a warrior race.
Split into simpler sentences: When he climbs back down, he exiles Loki from Asgard and then rallies the Asgardians to begin fighting back. To show their enemies why they are known as a warrior race.