Latias-Mega (F) @ Latiasite
Ability: Levitate
EVs: 252 HP / 4 SpA / 252 Spe
Timid Nature
IVs: 16 Atk
- Calm Mind
- Roost
- Psyshock
- Ice Beam
Tapu Koko @ Choice Specs
Ability: Electric Surge
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 23 Atk
- Thunderbolt
- Dazzling Gleam
- Volt Switch
- Grass Knot
Celesteela @ Leftovers
Ability: Beast Boost
EVs: 252 HP / 252 Def
Sassy Nature
- Heavy Slam
- Flamethrower
- Leech Seed
- Protect
I lead with Koko. I check if the Pokemon in front can be OHKOd with any of his moves, and if not I Volt Switch out. There are two defensive Pokemon in here. Celesteela is the physical wall, with this EV spread it gets Beast Boosts to Defense. Latias is the special wall. I usually set up a Calm Mind on passive Pokemon. If too many boosts are accumulated she can become a sweeper in her own right. Celesteela has a very good defensive typing and walls a good majority of Pokemon. Some of the problems I have been thinking about are Mega Alakazam (when Celesteela is down) and Mega Gengar. Mega Alakazam outspeeds everything in here and if it Mega Evolves, Traces Beast Boost and manages to pick off Celesteela then it is a terrifying threat. It also has coverage for my Pokemon, for example it gets Dazzling Gleam for Latias. Timid Gengar also speed ties with Tapu Koko, kills it with Sludge Bomb, kills Latias with Shadow Ball. Variants with Thunder also threaten to kill Celesteela. However Mega Gengar cannot directly switch in to Latias, who otherwise kills with a well-placed Psyshock.
I don't really have any form of priority so speedy sweepers can be a problem.
I use Heavy Slam instead of Flash Cannon for Minimise Toxic Blisseys which are commonly found in the Battle Tree.
I also don't have any physical attackers, so Calm Mind Pokemon with reliable recovery, such as Reuniclus, may be a problem.
Please help.
EDIT: Now that I think about it, Specs Magnezone is a problem.