Never posted in here before but I enjoy the story of D3 a lot and I just wanted to point this out.
Even though Zoltun Kulle is given the voice of a sadistic demon...his goals really aren't so terrible. He's trying to free man from its involuntary involvement in the never ending war between Heaven and Hell. Yes, I realize that he goes to some considerable lengths, albeit evil in nature, but I really feel like he's not as bad as the other villains in the story. I mean, he almost immediately knows about Leah, "I wonder if your friends know what you truly are." He recognizes Tyrael as the savior of man, and the embodiment of justice, "Whatever else he may be..." He encourages the Nephalem to rise above their petty tasks. He's just not so bad. And as SOON as he makes good on his word (which he COULD have broken as soon as he regained physical form), the Hero kills him... I don't know, I just feel as if he had potential as an ally.
Oh, and on a terribly unimportant/insignificant note, the Hunter's Journal Part 3 says that each step was "harder than the next." By that reasoning, he and his comrades should have had no problem getting through the Vault of the Assassin...I mean, if each step is easier and easier.... lol, probably just a goof in story writing.
Thanks for reading this, haha.
Zolten Kulle may have begun with the best of intentions but somewhere along the line he became twisted and sadistic, eventually desiring power for its own ends than to use it to save humanity.
We see where he started going wrong when he had to justify an incorrect position by rationalizing that the one vote to kill the humans was the same as if there was some massive public outcry in heaven calling for human blood.
But there wasn't. There was only a single vote cast to kill all the humans, 2 votes not to kill all the humans and 1 abstaining vote. 1 single vote to kill all the humans, and that 1 vote was Imperius who in all likelihood would have also voted to annilihate all the lesser angels too because let's face it, Imperius is a rapid dog. So that one vote can hardly be thought of as representing the majority of angelic opinion.
And if you go back and think about Kulle's aspirations you will notice that he didn't build the black soul stone to capture all 7 of the main evils, he only built it to capture a couple of demonic/angelic souls which he could then use to further his own power. While he attested that this power would be used to fight the angels and demons he never once presented a plan for how exactly this power was going to be used to stave off the great threat as he perceived it. Indeed he suggests to the player's character when no one else is watching that he will be able to use the new found power he will gain from the soul stone to turn you into a nephelem just like him if you will only look the other way.
He goes on to explain that the research that went into creating the black soul stone took a lot of sacrifice, and the suggestion is that it took a lot of human sacrifice for which he shows absolutely no remorse. The suggestion that Kulle sacrificed a lot of lives to create the black soul stone is reinforced by the dialogue you hear while gathering all the parts needed to resurrect Kulle where the Horadim went to such great lengths because they were very angry with him. Why were the Horadim so angry? Because Kulle killed a great many of their number to create the black soul stone.
Kulle isn't trying to save humanity from the angels and demons, he is trying to supplant them.
And to address two more points, Kulle shot first.
"I wonder if your friends know what you truly are." This was addressed to the player and not to Leah. Kulle had no idea that Adria was playing everyone for saps. But he did know that the humans were originally Nephelem, something which all of the humans have forgotten and now worship the Nephelem as gods (Akarat), and assumed that the player like the rest of humanity was unaware of this. Kulle wanted the player to believe that Tyriel knew the truth and wasn't telling the player the truth because Tyrael was using the player and was afraid the player wouldn't help him if the player knew the truth. This all leads us to believe that Kulle really isn't a nice guy because he tries to turn the player against Tyrael so that the player will help ressurect and then ally with Kulle against Tyrael. But we as the player with out of game knowledge know that Tyrael in fact is the one who is in the right in this instance.