Team Rocket has finally appeared in Pokémon Go—under the new name “Team GO Rocket.” They were first teased in the patch notes for the game’s latest update, then briefly appeared in the game earlier this week. Just as quickly as they showed up, however, Team GO Rocket suddenly vanished—in what Niantic tried to play off as part of the mysterious in-game event.

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

Now, it appears the Team GO Rocket grunts are here to stay, as they started taking over PokéStops and appearing in the overworld today. When a grunt invades a PokéStop, the usually blue photo disc is shrouded in black, with a red “R” over it. If a player interacts with a hijacked PokéStop, they can battle the grunt standing beside it. Team GO Rocket grunts use Shadow Pokémon in battle, which are Pokémon with glowing red eyes and a dark purple miasma swirling around them.

If the player defeats the grunt, they will have a chance to catch one of the grunt’s Shadow Pokémon with a special white Poké Ball. When they catch the Shadow Pokémon, they can “purify” it using that Pokémon species’ Candy and some Stardust. After purification, Shadow Pokémon will grow in CP and other stats, and will also require less Stardust and Candy to evolve or power up, because of the “gratitude they feel toward the Trainer who saved them.”

Along with this event, Professor Willow introduces a new Special Research quest called “A Troubling Situation” with Team GO Rocket-related tasks.

It’s unclear how long Team GO Rocket will be hanging around Pokémon Go, but it offers players an alternative way to encounter and catch Pokémon, as well as battle outside of Gyms or Raids. It’s a fun homage to the Pokémon Red and Blue, the first games to feature the iconic, villainous Team Rocket.

While this event unfolds, there are a couple other temporary features in Pokémon Go for the remainder of this month. Straw Hat Pikachu is available until 1 PM local time on July 29 as part of the game’s One Piece collaboration. Armored Mewtwo is also still available in five-star raids until 1 PM PT on July 31 to commemorate the release of Mewtwo Strikes Back: Evolution in Japan.