Strength Kensai magus with AC 22, 121 hit points with no Shocking Grasp or Frostbite tricks. He will use shocking grasp as a damaging spell but it is not optimized (straight 5d6 only). With Samsaran cheese he has dimension door as a third level spell and with the dimensional line of feats will try to do the Nightcrawler bouncing teleport attack thing on them.
What I need to know is if you think the party will have a chance against him or not. This is the largest group I have GM'd for and I'm a little out of my element. I am aiming for a challenging fight without killing anyone (that doesn't do something stupid anyway).
9 players against one enemy is a bad idea. It is better to use a larger number of lower CR creatures.
What I do is split the party in two. Make an encounter for each half, and then combine them back into one encounter, if I have 7 or more players.
Well that is how I used to do it, and it normally worked out.
I would use a CR 8 and a CR 9 encounter but split the XP up to have a least 5 bad guys.