one of my pc's is a pixie. we used the savage species book to set him up so according to the rules he's balanced. i've yet to decide if he is or not but whatever. here's the two part question:
one of the pixie abilities is to cast permanent image once per day, sound and image only. he used the ability to cast a globe of darkness accompanied by loud crashing noises centered on the head of a spellcaster.
1. would you allow this?
2. what would you set as the concentration DC for spellcasting?