Tan Chuduan was the fifth brother of the Quanzhen Seven and a senior member of the Quanzhen Sect. He is based of a real historical figure.
Fight with Huang Yaoshi and Mei Chaofeng
Tan Chuduan arrives with the rest of the Quanzhen Seven to fight Huang Yaoshi after their seventh sister, Sun Bu'er was humiliated by the former. However, Mei Chaofeng arrives and attacks the seven for trying to kill her master. However, through the use of Big Dipper formation, Mei Chaofeng was defeated but she was saved by Huang Yaoshi. The Quanzhen Seven attack Huang Yaoshi but are evenly matched and are eventually locked in a battle of neigong.
Ouyang Feng intervenes, killing Tan Chuduan and making the rest of the seven think that Huang Yaoshi did it. He then attacks Huang Yaoshi but the blow was blocked by Mei Chaofeng