For a short time, you will have a chance to catch Shadow Lugia in Pokémon Go. However, the only way to catch him is to make your way through Season of Mischief's special research mission, Misunderstood Mischief. The final tasks of the mission offer the opportunity to confront Giovanni, who now has the shadow Lugia under his control. After defeating it, you can catch this Legendary Shadow Pokémon. Here's what you need to know if Lugia Shadow is good and how to best use it in Pokémon Go.
Shadow Lugia is a Flying and Psychic-type Pokémon. It will be weak to Dark, Electric, Ghost, Ice, and Rock-type moves, but is resistant to Fighting, Ground, Grass, and Psychic-type attacks. As a Shadow Pokémon, Lugia receives 20% fewer defenses but gains 20% more attack. Traditionally, Lugia has an attack of 164, a defense of 256, and a stamina of 197, but as a Shadow Pokémon it has an attack of 196 and a defense of 204. While the defense drops dramatically, the increase in attack power makes Shadow Lugia even more lethal. However, the Pokémon's stamina remains the same.
Overall, the additional firepower available to Lugia's shadow is extremely useful. It was one of the things this Pokémon lacked, making it even more deadly in a fight. However, the sheer amount of defenses he had made it much more difficult to defeat. Even with losing 20% of defenses, Shadow Lugia still has over 200 defensive powers, making it problematic. But he'll have to be wary of Dark, Electric, and Ghost-type Pokémon that appear frequently in the Master League.
You'll still need to use the Shadow Lugia in the same role as the regular Lugia, which means having it as a Switch or Closer role on your roster. You can use it as a starter Pokémon, but other choices are far superior. If anything, Lugia's shadow is much closer due to the increased damage. The problem is whether it faces something that has super effective attacks against it. You'll have to be careful of those.
Shadow Lugia is still a solid Pokémon and lags slightly behind the original due to the huge drop in defense versus how much more attack power it gains in the process. We recommend Shadow Lugia if you don't have the original or don't have perfect IVs on your Lugia.