Apparently, it can detect the innate qualities of leadership. According to legend, whoever it recognizes is destined to become king.
– Pokémon Y Pokédex
Aegislash has turned from 2 swords into a sword and shield.
It has a unique ability, Stance Change, that allows it to change between its Blade Forme and Shield Forme. When it’s sent into battle, it starts out in Shield Forme. Using a damaging move will change it into Blade Forme, and while in Blade Forme, using King’s Shield (its signature move) will revert it back to Shield Forme.
Stat-wise, it has 150 in Def and Sp Def while in Shield Forme but only 50 in Attack and Sp Attack. In Blade Forme, it swaps its defensive and offensive stats.
Its signature move King’s Shield, acts like Protect in that it protects the user from any damaging moves (but not status); in addition, if the opponent used a contact move, its attack gets lowered by 2 stages. That’s why when going up against an Aegislash, it’s best to use Earthquake. I had a Contrary Malamar to counter Aegislashes, it was super effective; because of Contrary, Malamar gets an attack boost instead of drop when hitting King’s Shield.
Its typing of Steel/Ghost is still unique to its family.