You can kill them south of the trina fort wall along the battlefront, then they spawn along the southern path and get pulled back to the battlefront

Pieces 4-5

Locate at south of node "Trina Fort"
There has some glitch, if u can't deal damage just use Shai buff skills (or some specific moves for another class)
https://youtu.be/ZpebPRNimzI?si=wZd6jD_BosvUeQWd