A Mono Steel build where all six members share the Steel type. Steel's sturdy resistance profile covers Fairy/Dragon/Ice pressure at once, while each member's differing secondary type (Flying/Dark/Ghost/Dragon) spreads out coverage for Steel's weaknesses to Fighting/Fire/Ground. The whole point of this build is that a single Fighting-type STAB move can't sweep the team, since every member carries a different secondary typing.
Empoleon (Focus Sash): A tank that holds the front line with dual Water/Steel resistances. Focus Sash guarantees it survives one hit and hands the momentum to the Steel attackers waiting behind it.
Mega Skarmory (Skarmorite): A Steel/Flying sweeper candidate that's free from Fighting-type pressure.
Kingambit (Black Glasses): A Dark/Steel combo that's strong against Ghost/Psychic pressure, its Black Glasses reinforcing Dark-type power.
Mega Mawile (Mawilite): A Steel/Fairy dual-resist wall that firmly blocks the opposing Dragon line.
Aegislash (Spell Tag): A Steel/Ghost blocker immune to Normal and resistant to Fighting, with Spell Tag boosting its contact-punishing power.
Archaludon (Wide Lens): A Steel/Dragon combo whose Wide Lens corrects accuracy on its shakier moves for reliable damage. It's the team's last wall and closer rolled into one flexible card.