The result of Vauraki's wrath directed by Axtrami's will. The Sila'Khrysath is the elemental embodiment of the fury of the desert. Woe to those who encounter the Great Sand Wyrm within the Karikun Desert!
Worse than those of the Shattered Orb are those who have fallen from the Bright Path and Axtrami’s grace. Yet among them are some who have recieved the extreme blessing of Axtrami, to become glass themselves…
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