The official Pokemon GO blog has announced that the Legendary Pokemon Lugia is returning to Raid Battles in Pokemon GO. You can challenge the Legendary Pokemon until April 2nd.
“A powerful Psychic- and Flying-type Pokémon originally discovered in the Johto region, Lugia will appear in Gyms across the globe as the Legendary Pokémon Rayquaza returns to the ozone layer. You can challenge Lugia, which will know the newly improved Flying-type move Sky Attack, until April 2. So gather your strongest party to take on this Legendary Pokémon before it returns to the sea!”