Raids were recently introduced to Pokémon Go, and as long as you're at least
level 5, you can participate.
A special raid is happening in Chicago, however, a
legendary raid where a legendary Pokémon will make an appearance. Should
the Pokémon be defeated, then legendary Pokémon will be
unlocked for all players, beginning 23 June.
Thus all eyes will be on the trainers in Grant Park this
Saturday, to see if they can manage to beat
the Pokémon during the challenge windows that will
open during the event.
You can follow the festivities via YouTube or Twitch
however, and get a live reveal of which legendary Pokémon will be making an appearance. Once
legendary Pokémon are unlocked, then expect to
see Pokémon legendary battles where you could
score your own legendary Pokémon. However, these Pokémon will not be
able to defend gyms - so time to rustle up your
own Pokémon gym battling groups to prepare to take
down a legendary Pokémon.
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