This team dropped the previous Ghost-type cycle build that was vulnerable to hazard-stacking/setup development, and shifted to a stacking-oriented composition centered on Klefki — which handles walling and hazard-setting at the same time — while Taunt-set Mega Gyarados stacks Dragon Dance twice to make up for its lack of firepower. The reason for adopting Klefki is that it always carries one of Explosion-type moves/Taunt/Encore, allowing it to build up an early-game setup without opposition interference.
Garchomp (with same-type Focus Sash + Dragon Tail set) is used both as a check against firepower-oriented threats like Charizard and Mega Raichu, and as a pivot to substitute for Klefki, while the sub-Mega Glimmora shares the load against opponents that Gyarados is weak to. Sylveon (Yawn + Wish combination) buys time against wall-composition opponents while avoiding hazard-stacking, and Gallade (Life Orb) was added last to widen the range of options as a check against Mega Venusaur-line Pokémon and Greninja.