seeing dranosh saurfang lying dead or dying on the battlefield at the wrathgate and arthas spots him and
the clearest words he’s ever, ever heard in ner’zhul’s voice (because so much of the orc’s will is twisted and obliterated beyond coherence)
Arthas wouldn’t have listened to him anyway. The dude is stubborn.
Ner’zhul hadn’t been a voice in Arthas’ head for a long time by then. Since before we went to Northrend, Light’s Hope, and possibly the return of the horde/alliance military forces from Outland.