xedèkoP Meta
Metagame Premise: Pokemon’s Primary type is determined by the Primary type of their Dex Mirror.
Example:
#0002
————#1024
——-
Ivysaur and Terapagos are the Second and Second to Last Pokemon in the Pokedex and are Dex Mirrored. Ivysaur is a Grass/Poison type while Terapagos is a Normal type (or Normal/Normal). In this metagame, Ivysaur will become a Normal/Poison type, while Terapagos becomes a Grass type
For less obvious mirrors, you can do (total number of Pokemon + 1) - (Dex# of your Pokemon).
Like let’s take a Pokemon closer to the middle like

is #445 on the Pokedex, which means its mirror is 1026-445 or 581 which is

‘s Pokedex number. This means

becomes a Water/Ground type, while

becomes a Dragon/Flying type.
Also incase you were wondering what happens if we have odd number dex total, what happens to the exact middle Pokemon? In this case the exact middle Pokemon is

(513) which simply swaps with its mirror Pokemon also

(1026 - 513 = 513) staying as a Fire type.
Potential Threats and Bans:

Grass/Fire
Currently, Volcarona’s mirror is Torterra, making it a Grass/Fire type. This gives it STAB on its Grass moves but more importantly makes its defensive typing better. Volcarona is already a massive threat only held back by its typing limiting it a bit.

Electric/Flying
Dragonite is a great Pokemon currently, but is only getting better because its mirror is Morpeko, so it becomes an Electric/Flying type. This removes its x4 Ice weakness and also gives it STAB on Thunder Punch.

Water/Dragon
Hydrapple's mirror is Squirtle, thus it will become a Water/Dragon type, making it a really great regenerator Pokemon
Stinkers and Losers:

Electric/Ghost
Gholdengo’s Dex Mirror is fittingly Raichu, meaning that it’ll become an Electric/Ghost type. It’s still solid typing, but not remotely as good and means Gholdengo no longer spinblocks Mortal Spin.

Grass/Steel
Kingambit’s mirror is Oddish so it’ll become a Grass/Steel type, meaning it loses STAB Kowtow Cleave and Sucker Punch.

Water
Toxapex's mirror is Wingull. This is unique as Toxapex is a Poison/Water type, thus would become "Water/Water" type or simply pure Water. You lose out on Grass neutrality and many Poison benefits like its resistances or poison immunity.
Questions for the Community:
1. How should alternate forms work in this meta when the form changes a Pokemon’s typing? For example,

can change its primary type and is a mirror of

. What type should Grovyle be and what type should Silvally be with its memories?
2. Some Pokemon are simply no available. For example

currently does not exist in the game and mirrors

. This would mean that their respective types are Normal/Ghost and Bug. But with

not being available would it be fine to make

a Bug type despite that?
3. I use the national dex numbers as an example, but what about regional dex numbers instead? That would help with the second question and be more “official” I guess.