It can be dangerous trying to send someone a message. Spoken words may be overheard, written correspondence may be intercepted, and body language may be seen. Did you ever wish you could think the words and they would be known?
Gareth turned and squinted uneasily over his shoulder. He could have sworn he heard a high pitched hiss. He turned back to continue through the dim underground passageway. It was then that he saw them. A pair of ruby red eyes, glowing faintly a few feet front of him. He had to look up to see them, and that is saying something, given Gareth’s generous stature. The strike was quick…he had no chance. The last thing he remembered were the eyes hovering above him and the fangs dripping venom. And was that a second set of eyes gleaming beneath the first…?
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