Bassilus the Murderer would basically talk to himself, then to the zombies, who he thinks are his friends or comrades. He will think that you are his Father and you can play along and pretend you remember the old days. I understand that he left a group in the Zhentil Keep and they got killed while he betrayed them and ran, I guess that's why he is Chaotic Evil. If that is true then his action match the Chaotic Evil traits pretty well.
Since I attacked him and his undead straight away I didn't get a conversation with him. If you preted to be his Father you can make his undead army collapse and fight only him, just choose the top answers after he starts thinking you are his deceased Father :)
I missed my chance, although there is some pleasure in activating a Glyph of Warding on the undead lot :)
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