In Pokémon Shuffle, Gengar's Shiny coloration is significantly lighter than in the core series. Instead, it resembles Alva's Gengar from Volcanion and the Mechanical Marvel. Even your home isn’t safe. Gengar will lurk in whatever dark corner of a room it can find and wait for its chance to catch its prey. It evolves from Haunter when traded or when exposed to a Linking Cord. It is the final form of Gastly. It hides in shadows. It is said that if Gengar is hiding, it cools the area by nearly 10 degrees F. He says spiteful things, but he came to the Tech Area to look for his missing friends. He cherishes his friendships.

It steals heat from its surroundings. If you feel a sudden chill, it is certain that a GENGAR appeared. The Gengar pillow is absolutely reminiscent of Gengar’s Gigantamax form from Pokémon Sword and Shield. It’s in this form where his mouth takes over most of his body, as noted in the Pokédex:

Merry Gifting!

It hides in shadows. It is said that in rooms where Gengar is hiding, the temperature drops by nearly 10 degrees Fahrenheit. In Illusion Confusion!, multiple Gengar, along with a group of Haunter, were causing trouble for Ash and his friends while they were wandering through a deep forest, by creating a number of illusions that impeded their progress. It hides in shadows. It is said that if Gengar is hiding, it cools the area by nearly 10 degrees Fahrenheit.

In Volcanion and the Mechanical Marvel, a Shiny Gengar that can Mega Evolve was Alva's main battling Pokémon. However, it would abandon Alva immediately after the destruction of the Mega Wave crystal that controlled it.In Generation VI, due to a glitch, on the first turn of becoming Mega Gengar, it can still be affected by Telekinesis. In A Promise Given to Miltank, Morty called out Gengar to stop a Spearow from stealing the satchel that contained Berries collected by Gold. It apparently wishes for a traveling companion. Since it was once human itself, it tries to create one by taking the lives of other humans. Gigantamax Gengar's mouth is rumored to not lead into its body. Due to the cursed energy, it is believed to instead lead into the afterlife. By laying a trap, it attempts to steal the lives of those it captures. Should someone stand near its mouth, they can hear the voices of their loved ones calling out to them.