UPDATE 25th July: Team Rocket are back in Pokémon Go - and this time it appears to be for good.
The invaded PokéStops have returned in force, and Niantic has released an eerie new teaser to kick it all off.
It also made a new post today, stating: "Professor Willow and the team leaders have been hard at work observing and researching these happenings with Team Go Rocket, and they've come up with a plan to restore the PokéStops and rescue the Shadow Pokémon!"
Alongside Team Rocket's return comes a new quest to complete, A Troubling Situation, as well as some changes to Shadow Pokémon, which can now no longer be traded before they are purified.
UPDATE 24th July: Team Rocket seem to have vanished from Pokémon Go almost as quickly as they appeared.
In a tweet from the official Pokémon Go account yesterday afternoon, it was announced that the appearance of Shadow Pokémon has "suddenly stopped".
Professor Willow has noticed that sightings of discolored PokéStops and Pokémon enshrouded in a shadowy aura have...suddenly stopped? ? ? Hmm... This phenomenon keeps getting more troubling the more we investigate it. ?— Pokémon GO (@PokemonGoApp) July 23, 2019
The "discoloured" PokéStops were only spawning for around 24 hours before being shut off. It's unknown yet whether this is all part of Team Rocket's plan, or perhaps Pokémon Go needs just a little more time to work on the feature.
ORIGINAL STORY 23rd July: After weeks of buildup, the villainous Team Rocket have finally touched down in Pokémon Go.
Reports of their entrance began trickling in after 9pm UK time last night, as the first sightings of "invaded" PokéStops began. These Stops - which appear blackened and glitched - reveal a waiting Rocket grunt when approached.
Engage with the Rocket gang member and you'll be taken into a PVE battle against three of their Pokémon. If you win, you'll then get to catch a Shadow Pokémon the grunt has left behind.
Shadow Pokémon are a special type whose souls have been "closed off" by an artificial process. They're Pokémon made to do bad things by bad people, essentially. You can choose to keep said Shadow Pokémon as it is, all glowing red eyes and all - or you can pay a relatively small Stardust/Candy cost to Purify it, raising its stats.
Prepared for trouble ? pic.twitter.com/Ze13ct9OZT— Tom Phillips (@tomphillipsEG) July 22, 2019
There's a lot of new mechanics for fans to chew through here - our pointers on how to find Team Rocket in Pokémon Go can get you started - not least the ability to acquire two new forms of each Team Rocket Pokémon (Shadow and Purified).
So far, we've seen reports of Bulbasaur, Squirtle, Charmander, Rattata, Zubat and Snorlax as being available - although a datamine of the game suggests many more will be in the future. See our Shadow Pokémon list for what else might be coming.
More intriguing for hardcore fans is the ability to get great stats on these Pokémon species by trading them. Stacking the stat boost of a Lucky Trade and the further stat boost of Purifying a Shadow Pokémon gives a high chance of a 'mon with perfect - 100 per cent - stats.
But whether you care about stats or just collecting a few new things, it feels great to have a fresh feature in Pokémon Go after a relatively quiet 2019 so far - and a new reason to detour off your regular path to find something new.