When the overgod, Cain Lisworth, went insane, he lost his dominion over the universe as the overgod. That had created a ripple which mortals could sense or understand, and even some gods couldn't tell the difference, but Nyar and the abomination could. Like flies swarming a dying beast, they could just know the overgod was no more.
What made that worse was that the abominations had countless sleeper cells, agents, spies, and hidden nodes of power spread through the entire universe. In the same way the gods could explore the void outside the universe, the abominations were able to explore the inside. This was a war, and gathering intelligence was the most important need both sides had.
Nyar could've attacked immediately, but where would he attack? A reckless charge would only result in disaster. So, he waited for a few hours, days, and looked for any anomaly that could give him an advantage, and he soon found it.
