Elite Four

The Elite Four is the last challenge of each region consisting of four elite trainers and a champion. After gathering all eight badges of a region, the player must then defeat the Elite Four members and the reigning champion of that region. One after the other, relying on potions and revives to heal up between battles.

The Elite Four and gym leaders can also switch now. After using any debuff more than one time, you risk them switching.

Lance
Salamence holds a Mega Stone.

Hoenn Elite Four
All Hoenn E4 trainers' 6th Pokemon hold a Mega Stone. The Champion's Gyarados holds a Mega Stone.