The Regional Variants Game

[Devalue]

Frost Cavern in Kalos. Went there to hibernate. (Required a lot of observation to differentiate this from normal behavior.) Never bothered to leave.

Cricketune (Bug/Electric)

 

[ReKoil]

Blush Mountain.
Brought over by tourists from Sinnoh, they have survived by protecting Charjabug that are awaiting evolution. Constantly being near Charjabug has made it acquire the Electric type.

Cinderace (Normal/Fighting)

 

[Orion☆]

Bumpity bump before it goes in the dump!

Anyway, Floccesy Ranch. The Scorbunny line in Unova has been cross-bred with other rabbit Pokémon to create a variant that would keep pests away without burning the crops. That has also had the curious side-effect of making Cinderace's ears floppy, much like its Gigantamax form in Galar.

Eiscue (Ice/Dark)

 

[Devalue]

Castelia City in Unova. Comes out at night. Often steals valuable objects. Leaves a small umbrella in their place. Enlists other bird Pokemon, such as Pidove, to assist in these crimes.

Battles Woobats, Noibats, and Zubats at every chance. Runs away if things turn bad, though.

Swanna (Ghost/Flying)

 

[PokeDude645]

I'd say in the local ghost tower in your area, Pokemon Tower, Burnt Tower, Mount Pyre, Lost Tower, Celestial Tower, etc. But specifically Celestial Tower.

They would stare at you if you stood still for more than a few minutes. If you turned back they would attack you. But when you start moving they would phase through the walls and leave.
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Gallade (Electric-Fighting)

 

[ReKoil]

Chargestone Cave, using all the electrically charged rocks for training. Touching it will shock you. Glides through the cave at lightning speed using electromagnetism.

Hariyama (Normal/Fire)

 

[Fact Checking Gardevoir]

Mount Chimney - Some Hariyama came here to train under tough conditions in order to get stronger. But the heat prevented them from training in physical combat as much as they used to and they became Normal type. With time, though, they became attuned to the heat and developped Fire type!

Gardevoir (Ghost - Fairy)

 

[Devalue]

The Pokemon Tower in Lavender Town. Risked its life for the trainer and paid the price. Failed to save its trainer, however. Returned in a less corporeal form, perhaps due to resolve or regret. Supposedly seeks a way to change the past.

Solosis (Water/Psychic)

 

[ReKoil]

A group of Solosis lost the protective fluid they have and substituted it with ocean water. Over time their bodies adjusted and became part Water type. They can now freely swap out any water to replace their portective fluid.

Delcatty (Normal/Fairy)

 

[Devalue]

Route 6 in Kanto, just north of Vermillion City. Happens to be near the Pokemon Fan Club. Evolved differently with more affection for Pokemon nearby, sort of like Sylveon.

Kingler (Water/Grass)

 

[CF1994]

Brooklet Hill, Alola.

By feeding on the mushrooms of both the Paras and Morelull of the region, the Krabby and Kingler that migrated to Alola have developed a peculiar affinity for creating spores, as well as glowing like the bioluminescent mushrooms of Galar's Glimwood Tangle at night. They have gained the Sap Sipper Ability in large part to it's more vegan diet. Don't worry, the Alolan Kinglers ensure that the mushrooms of said Pokémon will eventually grow back with time every time they and Alolan Krabby would feast on them.

Lugia (Ghost/Flying)

 

[ReKoil]

In a secret cavern underneath Mount Pyre, only accessible from underwater.
It took refuge there while severely wounded and while on the verge of life and death absorbed as many grudges of those laid to rest there as possible.

Zangoose (Fairy/Poison)

 

[CF1994]

Glimwood Tangle, Galar.

To fend itself off better against swarms of obnoxious Impidimp, Zangoose harnessed the forest's fairy magic and any poisonous pathogens it received from many fights with Seviper to become a supernatural toxic avenger. However, it has left itself vulnerable to the psychic Pokémon that live there such as Indeedee, Hattrem, and the occasional Galarian Ponyta.

Seviper (Dragon/Poison)

 

[ReKoil]

Flying around outside the Dragonspiral Tower.
They prey on those who come to scale the tower and do fly-by's to whittle down their targets with poison.

Talonflame (Water/Normal)

 

[CF1994]

Route 9 + Lake Axewell, Galar.

Becomes a much thinner, slender bird Pokémon that acts as a crossbreed between an Albatross and a Canada Goose. These species of Talonflame migrated from a completely different region, but have somehow found themselves comfortable in Galar's cool, if occasionally frigid, lakes. They are highly territorial and hostile when there are Fletchlings to raise, so it is recommended to avoid getting too close to them, which is easier said than done due to the species' explosive surge in numbers.

Sandaconda (Ground/Water)

 

[ReKoil]

Ula'ula Beach in Alola; digging out into the water repeatedly has made it adapt to it. It digs around the beach and sea floor.

Carnivine (Bug/Poison)

 

[CF1994]

Viridian Forest, Kanto.

This cannibalistic flytrap disguises itself as a plant rich with nectar and succulent fluids that Caterpie and Weedle, as well as their final evolutions, often fall victim to. Attacking this Pokémon with brute force is a bad idea, as it will only firmly lock it's jaws even tighter to disrupt circulation.

Obstagoon (Normal/Ground)

 

[Devalue]

Diglett's Cave in Kanto. Previously felt satisfied with Snorlax blocking the entrance. Discovered Snorlax missing one day. Took up the mantle. Became frustrated with Digletts coming and going as they pleased. Evolved more Ground-type characteristics to block the Digletts.

Delibird (Dark/Flying)

 

[CF1994]

Route 9 + Frigid Sea, Galar.

The formidable wildlife of Galar's snowy tundras and oceans had forced Delibird to adopt more aggressive, underhanded tactics in order to survive the harsh wilderness, becoming more vulnerable to ice attacks in the process. It evolves into a Krampus-type figure very late at night that can do away with young trainers to a horrible fate if they don't know how to raise one competently.

It's Abilities would be Hustle and Insomnia, while Guts would be it's Hidden Ability. The final evolution, which I dub thee "Devillibird", switches Hustle for Intimidate.

Sneasler (Ice/Fighting)

 

[ReKoil]

Shoal Cave, Hoenn. Found in a newly discovered sealed chamber deep withing the cave. The Sneasler of ancient time hid here and ended up frozen. They ended up adapting to the Ice and freed themselves. They have lived in a tribal setting ever since deep inside that cave.

Exploud (Fire/Fighting)