Avengers Vol.1 #20
After jumping over the edge last issue, the Avengers have very little time to rescue Captain America, but with quick thinking they manage it; The Swordsman is outraged and attacks them. During the battle he starts to vanish mysteriously; He awakens in the lair of the Mandarin; The Mandarin allies himself with the Swordsman, giving him a more powerful sword; He then creates an image of Iron Man which he sends to the Avengers, vouching for the Swordsman's membership; Once in the Avengers HQ he plants bombs to destroy them; He later has a change of heart and tries to remove the bombs, but is caught by Captain America, who believes he is attaching them.
First Printing: Sept 1965
Writers: Stan Lee
Art: Don Heck and Wally Wood
Cover: Jack Kirby and Wally Wood