“ 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”
“ Sneezing Sickness - A strange plant infection that causes its victim to spread the plants seeds by sneezing them about. Larger lumps of phlegm or saliva sprout is spat out in a sunny place, producing more of the plants. As the Magical version of seasonaly allergies the affliction is limited in term and non-life threatening.”
“ A small band of squirrels seems to be fighting high up in a tree over a shiny nut-sized object. Can you retrieve the prize without scaring the squirrels into running off with it? If they do, can you manage to chase them down?”