Its not in d&d, but for some reason they put it in
If I asked, would you answer? Its your problem. Its a deep, deep problem. I have no way to ask about that... I have no elegant way of stepping into your heart without tracking in filth. So I will wait. Someday, when you want to tell me, tell me then. -Bleach
In AD&D, you can dual from anything to anything else, as long as you meet the requirements. No combos are barred.
[url="http://www.sorcerers.net/Games/BG2/SpellsReference/Main.htm"]Baldur's Gate 2 Spells Reference[/url]: Strategy, tips, tricks, bugs, cheese and corrections to the manual.