This is my second collaborative battle guide! Normal Mode is always covered, and anyone can do Easy & Hard mode.
Any decent ice, dragon, or fairy type will take him down easily. For his second fight, bring a good ground or ice type. I recommend the delta versions of metagross (spider) and either delta gard or delta Gallade.
Jaern - The first battle is easy. A good Ice-type like Delta Garde/Gallade easily kills, especially with choice scarf. For the second battle, Ice type is only good against half of those pokemon. And a ground type takes care of the other half.
Audrey - Choice Scarf. STAB Freeze-Dry. The first battle is over. The second battle, you can use the same strategy, but bring a strong Ghost/Dark/Bug Physical attacker for alakazam.
Zenith - Choice Scarf Excadrill does well in BOTH FIGHTS! What? Only Volcarona is an issue for it, which in that case you can go get a nice rock type move, STAB if you really wanna screw it over.
Persephone - A good fairy type sweeps most of her team the first go around. The mega gengar is actually a Mega Zoroark, so watch out! For the ACTUAL Gengar, use a pokemon like Delta Ambipom. For the second and third battles, a good Dark type takes Gengar, Metagross & Alakazam, a good Fighting type takes on Houndoom & Hydreigon, (fairy works too) and for that Spiritomb? Once that noctem is over or another weather is set up, a Fairy-type pokemon could go in for the kill. If not, use brute force.
Reukra - For the first battle, I’m gonna bring a quote from my edit from the E4 Guide.
For the second one though? The battle is so EASY! Just exploit all of the double weaknesses his party has with a good pokemon. D. Goodra is Grass, Armortar & M. Bisharp are Fighting, Noivern is Ice, and S. Mewtwo is Bug. Mold Breaker Excadrill finishes off Armor Darona. (Delta Volcarona)