Quote Originally Posted by Ouch! View Post
Ed, if you want more intelligent/formidable/aggressive enemies, obtain and activate the following: Mythic Skull, Tilt Skull, Tough Luck Skull, and Thunderstorm Skull.

That'll double their HP, boost their resistance, guarantee saving throws, and increase all enemies' rank if possible.

Incidentally, activating the Catch Skull and the Cowbell Skull at the same time makes for lots and lots of fun.
I can't be bothered to go around and get the skulls...well...I can but that is for achievements XD Those don't sound like they make the enemies more intelligent though. Maybe rank does but what is 'rank' O_o