The battlemage is smoking that golem. The Necro can do just as much damage to the Battlemage with the army. A flashfire would have made the difference in this fight. From what I've seen and heard about this thread. Looks like they both had had enough and just went for it. I'm sure the battlemage was shocked when the illithid was able to do that in combat. I don't think other necros can do that while they're fighting.
I know I tried to do it with Puerilaug when fighting the beast ranger in Warmaster and could not do it. But if you notice that low dex is destorying the illithid, thats why its able to do all those fun things.