Brainiac has acquired The Golden Army from Prince Nuada, he then discovered a portal leading to HxH Verse seeing how civilizations flourished in this reality he then formulated a plan to study and possibly conquer this said civilizations, he recruited Harald Jaekelsson and his band of undead vikings promising them cities to conquer & pillage.
after arriving at lake mobius, they then proceeded to rape and pillage Yorknew City and killing every hunter inside the city
But after reassessing his options, he and Jaekelsson decided that they will conquer the entire Lake Mobius by any means necessary.
The Hunter Association is now fully aware of the invasion and mobilizes its hunters. if necessary the hunter association can mobilize the best of their hunters from the start if the invasion is considered dangerous enough to endanger whole of humanity
If the invasion is strong enough the criminals/villains in hxh verse would logically team up with other hunters to defend against the invaders
So, How would Hunter Association react to this? what countermeasures would the association enforce/plan?
And what strategy would they use to contain/eliminate this apocalyptic threat?