Pokémon GO launched just over a year ago, and instantly became a cultural phenomenon. Its popularity has waned since then, but there's still a dedicated player base. Those still venturing out to play Pokémon GO will soon be able to capture legendary Pokémon, which have been conspicuously absent since launch.
Legendary Pokémon are much more powerful than other Pokémon; so much so that they were never added to the game because of balance issues. Now, they'll debut as bosses in special legendary Raid battles. Niantic added this game mechanic a few weeks ago, which involves defeating a super-powerful Pokémon that periodically appears at gyms. See the video below, which makes Pokémon GO look considerably more exciting than it is.
When a legendary Pokémon shows up in a Raid Battle, players who defeat it will have a chance to capture it. How good that chance might be is not clear. Should you snag a legendary Pokémon like Moltres or Articuno, you can use it to battle in gyms. However, you cannot leave it to defend a gym. Niantic has made several changes lately to encourage more turnover in gyms, so putting a nearly unstoppable Pokémon in there would be counterproductive.
The first legendary Pokémon will begin appearing in the game this weekend with a kickoff at Grant Park for Pokémon GO Fest. That Pokémon will only begin appearing in other Raid Battles if it's defeated at the event.
- Pokémon GO Live