I have been following along with Truegreen7's series on Youtube where he and 3 other Fakemon artists get together to design a new pokemon based on the same prompt.

This Prompt was: Dependant Evolution
These pokemon's evolution is dependent on being with one another like Slowpoke and Shellder joining to becoming Slowbro. I wanted to use the concept of my own Charmander and Gastly duo, Sunny and Noctis as inspiration for these pokemon but made them their own stand alone Pokemon species. I knew I wanted to make them a cute little lizard who's best friend is a funny ghost so I decided to work backwards from some of Charmander and Gastly's own inspirations.

The Charmander family possibly is partially based on an obscure bit of Medieval German Folklore, a small Friendly Dragon or Dragon-like Spirit called Gluhschwanz (German for "Glowing Tail" because the end of its tail glows and makes it appear to look like a Shooting Star when it flies around at night) who will be your friend if you feed it Cheese, and go around stealing coins and trinkets from other people's houses and bringing them back to you. We'll put a pin in that for later

This got me thinking of another creature from German Folklore, Kobolds! Kobolds were not always cute little mini-dragons but thanks to the popularity of D&D the association with Dragons has pretty much stuck in the modern popular consciousness. Sometimes they could appear as a Ghost, a Child-like Fae creature, a Goblin, A Nature Spirit, Animals, a Ball of Fire etc...So basically all encompassing supernatural being, but I decided to lean into the Kobold's association specifically with Fire and Mining. Kobold pranks would be blamed for things going wrong in mines, including being able to Poison Metal Ores, lending their name to the metal Cobalt which is Poisonous! Let's put another pin in Kobolds being Prankster Spirits...

Koalmolt (Fire/Ground) is a helpful little Kobold who yearns for the mines. It has a Shovel for a tail and a little candle flame on its head that helps it light the way through dark caves.

Kobotage (Fire/Steel) is a mischievous older Kobold who if they can stay on task are very industrious workers but they can easily get distracted and like to mess around with things leading to accidents in the workplace

The otherside of the table is the pokemon inspired by Gastly. Gastly is a Ghostly ball of Gas which is based on Will-o' Wisps, ghostly balls of fire that lead people astray. This got me thinking of another Ghostly Fire, the story of Stingy Ole Jack. For those who are not familiar with the story, the short version is;
Jack was an old man who kept pulling pranks on the Devil himself in order to force the Devil into impossible to escape situations and wouldn't release him unless he gave Jack more years on earth. The Devil who became fed up with Jack's pranks eventually banned him from entering Hell. Jack ended up living a very long life but because he was still a jerk he was banned from entering Heaven too and had no place to rest in the afterlife so he took an ember of hellfire and put it in a Turnip to light the way where he wandered creating the first Jack o'Lantern!
(Once again we have another Prankster)
The Pre Evolution could be seen as a cartoony floating skull with flame eyes, or a Turnip, and because of the association with Jack o'Lanterns, Stingy Jack is sometimes connected with characters like the Headless Horseman and the Dullahan so I made the evolved form appear like a headless ghost-man but instead of being gorey he has a ghostly flaming eye where his neck should be.

Grimlow (Ghost) is a shy wandering spirits that give off a ghostly light. They will often run away from people on sight prompting curious people to chase them and get lost.

Gheistro (Ghost) is no longer afraid of people but likes to appear before them in a sudden puff of Smoke and fire as well as performing other tricks to get a rise. It will sometimes hold a Grimlow on their head and pretend to be a human and then tear it off to make people scream.

So far we have a little dragon who flies between houses at night, two different sorts of mythical pranksters in Kobolds and Stingy Jack, and the Origin of the Jack o'Lantern, so this is all starting to feel very Halloween themed! I decided to make their combined evolution a funny little Trick-Or-Treater Dinosaur-like creature wearing a classic sheet ghost costume that's an actual ghost!

Hallowyrm (Fire/Ghost) are a very rare pokemon who evolve from a Koalmolt and Grimlow in the party at max friendship but only at Night and in the Autumn leading up to Halloween. The Koalmolt and Grimlow in this pokemon are best friends who want to celebrate the Spooky Season together.