Game master tip #1 byRather 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
Ideas - Articles
January 29, 2015
“ Next time you're contemplating a horse variation, but don't want to get too dramatic, how about a Zorse? An offspring of a zebra stallion and horse mare. In nature they are infertile, but in a fantasy world, not necessarily. They are also known to be extremely cantankerous. 'It soon became apparent that zorses are not the most easiest of the equine family to get along with.' -- Trainer Pat Parelli, on working with zorses”
“ He's a non-descript man, with his pushcart. On it he sells nothing more exotic than jars of sun-dried tomatoes in oil and pickled vegetables. But he's always out there, in the courtyard of the great Guild of Wizards, in most weathers, and he'll have a kind word for you, and a jar.”
“ On the road up Dethl Mountain, you will encounter the guardian, Rustus, a goron Pyro Mage. only those who can take the heat will withstand him. to defeat him, one must use a goron's worst enemy: water”