Battle Pavilion preparation
Attempt1 lost in round3 to Knight Seyon. R1 Evevee (Houndoom/Shiftry/Leavanny) and R2 Theo (Vileplume/Nidoking/Toxicroak) won without items. Seyon Heatran revealed Magma Storm/Toxic/Stealth Rock/Protect, Air Balloon. Cresselia was worn down, then Excadrill Earthquake KOed her through Levitate and swept Magearna/Heatran. Never repeat the original triple weakness blindly.
Retry: Mienshao (Wide Lens; Reckless High Jump Kick/Fake Out/Acrobatics/Wide Guard), Magearna (Trick Room/Calm Mind/Dazzling Gleam/Flash Cannon), Cresselia (Calm Mind/Psychic/Trick Room/Moonlight). Level100 healing automatic each round. Use Fake Out + HJK to break sashes against suitable targets. Preserve Cresselia for Ground attackers and boss.
Boss218 installed DEFNOT/Mewtwo1000, Rainbow field. Cresselia can set Calm Mind on Probopass (SR/Discharge/Flash Cannon/Earth Power; Sturdy/Air Balloon), immune Ground. Heal before low HP. Psychic at +6 should beat Amoonguss (Spore/Giga Drain/Toxic/Venoshock) quickly and threaten MegaMewtwoX (Drain Punch/EQ/Ice Punch/Psystrike). Chesto covers one Spore; watch paralysis and PP. Magearna backup.
All5 rounds restart after loss; no reload used. Facility autosaves at entry and continuing (installed OrgBattle.rb). Mienshao selection proof and fresh own snapshot must be captured after prep. Major attempt counter starts at actual fifth-round attempt; first run never reached it.