Uxie, Mesprit, and Azelf Pokémon GO will be available to battle in Raids during the Lake Legends event. Here's what you need to know to take these three down and claim them for your collection.
Each of the Lake Trio is exclusive to certain regions of the world. Normally, you're stuck with the one that's for your area but you can use Remote Raid Passes to battle the other ones.
Uxie, Mesprit, and Azelf Pokémon GO: How to Counter the Lake Legends
The Lake Legends are pure Psychic type Pokémon. In general, a strong Dark or Ghost type Pokémon like Mega Houndoom or Mega Gengar will make short work of them. If you choose to use Pokémon like Weavile or Giratina, you'll have to watch out for some type covering moves the bosses may possess.
Uxie is available normally in Asia-Pacific. Its cover move is Thunder, so avoid sending out Flying or Water type Pokémon against it. It shouldn't give you any problems, as there are very few Dark or Ghost types that are also Water or Flying.
Mesprit is found in Europe, Africa and the Middle East. It knows Blizzard, which would ruin your day if you're using the Dark/Dragon type Hydreigon or the Ghost/Dragon Giratina against it.
Azelf can be battled in the Americas. Fire Blast is one of Azelf's attacks, but most of the best Dark types like Mega Houndoom and Hydreigon will resist it anyway. Watch out if your Dark attacker is Weavile, as the half Ice type will make it take massive damage.