The chair was used by Kang to explore Captain America's timeline during World War II as he witnessed Cap's battle against HYDRA and Red Skull and Steve's fall into the ice after Bucky pushed him to save his life and then perish in the explosion.
However, when Kang watched the battle, Bucky was getting suspicious about something or someone is watching them.
Kang used his chair to attack the Avengers and transported them to future Earth's ruins where he told them that Captain America's responsible for all of the destruction. He demanded them to surrender the World War II legend to him but refused and fought him.
As Kang fought the other Avengers, Iron Man had gained access of his chair and explained to Kang that his future technology is based on Stark Industries technology. Stark then transported them back to their own timeline. As Kang is about to make him pay for hacking his chair, Iron Man put up the shield around the chair, nearly shocking him.
After Kang's first defeat, he was ordered to surrender, but the latter contacted Damocles to recall him and the chair. As he returned back to his mothership, Kang was angered by the Avengers' resistance and decided to show them of how he earned the title Conqueror as he brought all of the Scarab fleet into the 21st century Earth to begin his invasion.