The fight against xivu isn’t impossible. Fighting makes her stronger but their is one tactic that can prove effective against her, self sacrifice. In the lore (I forget the name of the tab but it’s in Weblore) pre savathun possessed Osiris goes to the moon near the beginning of season of the hunt. Their he gets into a fight with the Will of Xivu Arath. His light gets suppressed by darkness and it gets stronger the more he fights. That’s how he loses Sagira, she basically blows herself up to save him and that cleanses all the darkness in the area and gets rid of the Will of Xivu Arath. Shortly after this he gets possessed by the witch queen. Basically this means kamikaze tactics should be effective against Xivus forces. This will probably become relevant at the end of the season, I think to push back the wrath born Rasputin will somehow sacrifice himself, completing his narrative arc, but only after informing us of neoluna