Fang Danyun is one of the minor characters in I Shall Seal the Heavens.
He is a member of the Fang Clan and its' only Tier-9 Alchemist in all of the Dao of Alchemy Division of the Fang Clan and, thus, its leader.
He is seen as a kind, compassionate, honest, and a genuinely good person. He supported Meng Hao after he saw the talent in him, and didn't think for a second giving up the position of the Head of the Dao of Alchemy Division of the Fang Clan to him after he realized that Meng Hao's skill far surpassed him.
During the Fang Clan Civil War, Fang Danyun appeared to save Meng Hao from the Quasi-Dao Realm Ji Clan members. After unlocking a seal which sealed his Quasi-Dao Realm cultivation away, in exchange for his longevity, he was able to fight against the other Quasi-Dao Realm cultivators. With the help of the Terracotta Soldier, he managed to repel the Ji Clan's Quasi-Dao Realm experts.
Afterwards, he, along with everyone else in the Fang Clan, bowed to Meng Hao after he "concocted" the number one pill of the Fang Clan, which no one, except the First Generation Fang Clan Patriarch, was able to.