https://www.polygon.com/2018/10/23/18015184/pokemon-go-halloween-2018

This year’s Pokémon Go Halloween event will highlight the freshly released generation-four Pokémon. No, it’s not just Bidoof getting the spotlight: Starting on Oct. 23 and continuing until Nov. 1, ghost- and dark-type Pokémon from Sinnoh — such as Drifloon and Stunky, which will make their first appearances — will pop up more frequently. Trainers will also earn double candy for every Pokémon caught.

There’s also some special research tasks from Professor Willow, focusing on a mystery Pokeémon roaming around Professor Willow’s lab after he found a strange stone. The tasks will highlight all the spooky-scary dark- and ghost-type Pokémon that roam the world.