I did a few more tests in an unmodified game.
"LICH01" is an ordinary lich--for example, the kind that appears in the Shade Lord's dungeon if you have a high level party. In an unmodified game, the lich is 11th Level. (With the improved lich MOD, the lich is 25th Level.) I made the lich explode with an 18th Level Cleric.
"HLDEMI" is Kangaxx the Demi-lich. He's 27th Level. Contrary to my previous post, you can indeed make him explode if your Cleric is 34th Level. I didn't know that before, and to be honest, I'm surprised that he's vulnerable to that form of attack. I think the reason why Kangaxx's first form can't be turned is because it would break the quest if you could do so; otherwise, I don't think it should be seen as a special form of immunity. In other words, if it didn't interfere with the game, you could probably turn Kangaxx's first form.
"HLSHAD" is the Shade Lich, and "HLLICH" is the Elemental Lich. They're both 20th Level. I made them explode with a 27th Level Cleric. To be honest, I used to think they wouldn't explode because I thought they were in the "special" category, just like Kangaxx, but I was wrong about all of them.
To be honest, it wasn't my intention to put forth the "theory" that you can make undead creatures explode if your Cleric is exactly seven levels higher than the monsters. The people who made BG2 have a tendency to bend rules and customize monsters, so I wouldn't expect them to stick to such a rigid scheme if they had a reason to break from it. But from looking at the results of my tests, the "Seven Level Rule" appears to hold up for most of the monsters, so I guess you can use it as a general guide.
I hope you don't mind if I don't comment on the cheese that some of you are talking about. Cheese impresses me sometimes, but I just don't know what to say.
