“ 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”
“ In some regions, various occupations might be exclusively staffed by members of a particular race or ethnic group. As examples, a city's butchers might tradtionally have orcish blood, or all the dwarves in an area could be expected to join the miners' guild (even if they personally have nothing to do with mining). Those who violate these stereotypes may find themselves in conflict with local customs or idiosyncratic laws.”
“ The PCs have been traveling for a long time down the same stretch or round with no sign of anything suspicious. As they cross over to the next hill they see a gigantic splater of blood with a bleached dragons scull in the center of it. It the dragon skull's mouth is a tattered backpack with something wiggling inside of it.”