Tandemaus and its evolution Maushold are new Pokémon coming to Pokémon Go as part of July 17’s Ultra Unlock: Better Together event. Finding one, though, is perhaps more complicated than it needs to be.

From 10am on July 17 until July 22 at 8pm local time, Tandemaus is available to catch for a limited time, but you wouldn’t know that if you looked at the overworld. It won’t spawn in the wild but instead has a unique way to find and catch it. So best of luck, trainers—you’re going to need it.