Would a 24 Fighter / 20 Mage who casts Black Blade of Disaster have the thac0 of a level 24 Fighter, or have the thac0 of a level 10 Fighter.
That is when the blade sets your thac0 to the thac0 of a fighter of half your mage levels, does it take the highest of your current thac0 and that new number, or does it overwrite your thac0 with the new number even if that would be bad?
That is when the blade sets your thac0 to the thac0 of a fighter of half your mage levels, does it take the highest of your current thac0 and that new number, or does it overwrite your thac0 with the new number even if that would be bad?