A college campus for modern day settings, where things are more than they seem at first glance. (Good for a horror or mystery setting)
I would have never had thought one could come to like a rattling pile of walking bones, but Tohm simply grew on me. Watching him play checkers with Formuro was always amusing - whenever he took one of Formuro’s pieces he would rattle his jaw in joy.. From the diary of Professor Ethric, faculty of Divination.
Rather than making a baddy impossible to hit, consider giving it mega-hit points.
Super hard to hit leads to great player frustration. Allowing them to do damage leads to a sense of accomplishment. another variation of this would be to give the bad guy a forcefield that shows damage.You could also give them a mastermind ability that sluffs the damage of to minions who should be easy to kill.Once in a while a super high to hit encounter is ok ,but it should be few and far between.
Your mileage may vary