Countless demons and monsters swarmed in from the opened portals like a flood.
Apart from some of these demons that were summoned directly from the Burning Hells, the rest were almost all from all over Sanctuary. Diablo and the other demon kings had been operating in Sanctuary for many years, and the dark power they left behind had corrupted a large number of creatures, causing the number of monsters to be astonishing. Roy's Demon Eyes had stayed in the wilderness, and once he opened portals, they attracted these guys.
Even ordinary monsters, out of disgust for the power of holy light, couldn't help but charge with the demons after arriving in the High Heavens. With such a large number of demons and monsters gathered together, the contamination of dark power was terrifying. This dark power in turn stimulated their bloodthirsty instincts, so on the battlefield, the army of the dark camp was crazily launching tsunami-like attacks on the Silver City.