Apparently, something big would happen once he ascended godhood.
Nial had yet to talk to Damian about this, but the most recent memory he had acquired from the late God of Darkness were a few words he had spoken to his subordinates.
The words invoked something deep inside Nial, and they made him feel uncomfortable, to a degree that he was pretty sure his ascension would lead to war.
[When the time is ripe, and a new star of darkness ascended the ladder of godhood, come out and fight next to your reign and master!]
Others might not think too much about those words, but Nial knew better. He could tell that the Late God of Darkness didn't want to fight anymore. However, at the same time, it was obvious that Damian had been dissatisfied and that the last Advocate of the Pryards had to be killed before Damian was able to rest in peace.