Basically, Aegislash:
- was a great stall & wall breaker
- could run mix sets and therefore mean that there was no safe switch in and not rendered useless with Will-O-Wisp
- has great typing
- has STAB priority <---this alone+ 50/50 King's Shield balance game...
- while not possessing an exactly thrilling movepool, has all the moves it needs to be effective, much like Excadrill
- is a brilliant Fairy counter in the current metagame
- has great ability and a priority move that allows it to go offense/ defensive at will, unlike, e.g. Meloetta, who doesn't get priority with Relic Song and is blocked by ghosts