“ All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.”
“ 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”
“ These little beetles have heads at both ends of their bodies. This allows them to feed on leaves at twice the rate of their normal cousins, causing great damage to crops. They look like ladybugs more than actual beetles, but have no wings. They have a funny way of moving if one stops to watch them, as both heads seem to vie for picking the direction at any given time. Their favorite nourishment is sugar cane. After feasting on these for some time, they develop short bursts of frenetic energy, and can be seen racing back and forth without purpose, which looks quite comical to onlookers. They are otherwise normal bugs. Of course the pc's might not know that.”