The concept is to create a numerical advantage with an early Mega, then finish with two Pokémon that have high face-to-face performance; this season it was expanded into a three-Mega system with no non-Mega Pokémon. As the first Mega, a Fighting/Fire type combining firepower and speed was adopted; as the second, the face-to-face-oriented Water-type Mega carried over from the previous build; as the third, a Mega (Poison type, holding a transformation-type consuming move) was adopted to handle the Water-type opponents that both of the other two Megas are commonly weak to.
The basic selection is one of the three Megas that fits better against the opponent, combined with two of the remaining two high-face-off-power supporters (Steel/Ghost). The Steel type buys time by putting the opponent to sleep or using Curse + Protect, while the Ghost type finishes off the remaining HP with shadow-type moves — a division of roles. The third Mega increased its HP investment to maximize the damage of its transformation-type consuming move, and when needed, it is also used to deceive the opponent by inducing sleep.