[JR Jansen]

Try summoning some stuff. Noteable here are Nishruu's and/or Hakeashar's. Get your best fighters to keep Jon's attention while your mages are summoning. Then pull everybody out of Jon's sight. Because this is primarely a magic battle, the nishruus should hold out long and absorb some if not all of his damage. If one gets killed, due to a death spell or something, just summon another. Don't worry about loosing out on items because once the battle ends, you'll be transported immediatly so you can't pick them up anyway.