C1777 Dantian space
Although Black Heavenly Treasure Charms s were talisman s, they were actually not true immortal artifacts. They could only be considered to have the dao tools of the Immortal Path's laws. Since it was not a real immortal equipment, then Qin Lang saw it as having a weakness.
Qi Long's venom attack was designed to deal with the Black Heavenly Treasure Charms's weak points