I was re-reading the description of Cause Fear, and it raised a question. Are creatures with 6 or more HD immune to the entire spell, or only immune to being shaken if the successfully save? Here's the entire text:
"The affected creature becomes frightened. If the subject succeeds on a Will save, it is shaken for 1 round. Creatures with 6 or more Hit Dice are immune to this effect."
"The affected creature becomes frightened. If the subject succeeds on a Will save, it is shaken for 1 round. Creatures with 6 or more Hit Dice are immune to this effect."