Yazneg is first seen spying on Thorin and the other dwarves, after they make camp in a rocky outcrop in the Lone-lands. Yazneg then orders his lieutenant, Fimbul to report the dwarves location back to their master, Azog.
Later he is seen leading an all out assault on the Dwarf party in an attempt to kill their leader, Thorin, however the orcs are distracted by the wizard, Radagast the Brown, used his rabbit pulled sled to outrun the Orcs and their Wargs. This distraction does not last as Yazneg is able to detect the Dwarves and focuses his attack on them in a last ditch effort to claim the head of their leader, Thorin Oakenshield, for his master. Just as Yazneg and his Orcs strike the Dwarves in their hiding spot, Elrond and his Elvish bodyguards arrive and kill many of the attacking Orcs and Wargs causing Yazneg and his subordinate, Fimbul, to flee for their lives.
After being ambushed by the Elves and failing to kill Thorin, Yazneg and Fimbul travel back to Weathertop, where the Orc hunters have made their camp. After explaining the situation to Azog, the Pale Orc coldly rebukes that if Yazneg had failed then he should have died in the process - Azog then chastised the Orc captain by picking him up and throwing him to a Warg nest where the Wargs devoured him violently.