Just a few cents worth with quotations. The Book of Exalted Deeds says fairly clearly in chapter one that murdering a surrendering foe is an evil act. It also details how to go about seeking redemption for that act.
Page 7, Mercy, Second Paragraph:
Page 9, Ends and Means, Second Paragraph...
For prime creatures I prefer hobgoblins. A highly regimented society combined with their tendency to bring their cousins under their control makes them seem much more menacing than a orcish horde. They can be smart as any human or dwarf, so I can also see them using technological advances to...
Naive response for the day
Are we sure this isn't a simple answer hidden in pretty packaging? I mean, a really evil villain might just make sure that all the blanks removed were the same symbol to make it easier for the henchmen, but lay it out in a complicated manner to fool intruders.