Raid Battle

A Raid Battle is a special event that takes place within a Gym in Pokémon GO.

Details
A Raid Battle is a cooperative gameplay experience that encourages Trainers to work with other Trainers to defeat an extremely powerful Pokémon known as the Raid Boss. Before a Raid Battle begins a large egg will appear atop the Gym. When the countdown above the egg reaches zero, the Raid Boss will be revealed.

There is also a special Raid called an EX Raid Battle which is an invitation-only Raid. A trainer will receive a notification along with with time, date and location; along with an EX Raid Pass to gain entry into the Raid.

Eggs start to appear at 5:00 AM and end at 7:45 PM local time.

Raid Passes


Before a Trainer can battle the Raid Boss, they'll need a Raid Pass. Trainers can receive one free Raid Pass per day by visiting a Gym, but can only hold one at a time. A Premium Battle Pass may also be purchased from the in-game Shop. Players can also battle the Raid Boss remotely using a Remote Raid Pass.

Raid Boss
A Raid Boss or Boss Pokémon is an extremely powerful Pokémon that has very high CP. It hatches from a egg which appears atop a Gym upon the beginning of the Raid Battle. A countdown will display the time until the egg hatches and the battle begins.

Upon using a Raid Pass to join the battle, the Trainer and up to 19 other Trainers work together to defeat the Raid Boss. If a Raid Boss is successfully defeated within the three-minute time limit, or five-minute time limit for Legendary Raids, those Trainers have the chance to catch a decently powerful Pokémon of their own. The captured Pokémon does not necessarily have the same moves as the Raid Boss.

A Raid Boss can battled as many times as possible before it is either defeated or the 45-minute time limit expires.

List of Raid Bosses
There are a limited number of Pokémon that can be possible Raid Bosses at the same time.

The pool of available Raid Boss Pokémon have been changing since the feature release. Additionally, in past events, there have been exclusive Raid Bosses that cannot normally be encountered in Raid Battles. Some Raid Boss Pokémon had even their Tiers changed.

Raid Boss CP formula
The formula is identical to the traditional CP Formula; except the stamina and CP scalar portion in the divisor are replaced with a tier scalar which represents the Raid Boss's HP and the IVs for attack and defense are fixed to 15 (maximum IV value).

$${BCP = \frac{(Base Atk + 15) ~ \times ~ \sqrt{Base Def + 15} ~ \times ~ \sqrt{TierScalar}}{10}}$$

Where   is:
 * Tier 1:  
 * Tier 2:  
 * Tier 3:  
 * Tier 4:  
 * Tier 5:  
 * Tier 6 (marked as 5):  

Tiers of Raid Bosses
Tiers are simply difficulty levels of Raid Bosses. These Tiers are distinguished with specific Raid Eggs which hatch into Raid Bosses. Upon the beginning of countdown for the Raid Battle, a Raid Egg will be placed atop the Gym. A countdown will display the time until the Egg hatches and the Raid Battle begins.

A Raid Egg will usually appear one hour before it will hatch. Certain events will decrease the time of hatch time. The Raid tab in the Nearby Tab will denote the hatch time in 24-hour clock or military time. Once the Egg hatches, the Raid Boss will become available for battling for the next 45 minutes.

There are four kinds of Raid Eggs – Normal, Rare, Mega and Legendary, each of the Eggs represents another Tier of the Raid Boss.

Rewards
Completing a Raid Battle for the first time will always award 1,000 Stardust. After defeating a Raid Boss, Trainers receive a collection of rewards which depend on the Tier of defeated Raid Boss.

Bonus Challenge
Bonus Challenge is a feature available for Trainers who successfully defeated Raid Boss and it gives an opportunity to catch the Raid Boss Pokémon as if it was a Pokémon in the wild, but with a significant difference – Trainer cannot use their owned Poké Balls.

After successfully defeating the Raid Boss and being rewarded with Items, there are Raid Battle performance statistics shown to Trainer with amount of Premier Balls given to them and the button displayed.

After tapping on the button, the encounter screen shows up with Pokémon that is a defeated Raid Boss. The player does not have their currently owned Poké Balls for use but only the Premier Balls that they have been rewarded for performance in won Raid Battle.

Pokémon in Bonus Challenge, especially Legendary and Mythical Pokémon, tend to dodge and attack more frequently and have low capture rate.

If Trainer do not manage to capture the Pokémon with their last Premier Ball and there are no more Premier Balls left, the Pokémon will flee.

Trainer can leave the encounter screen of Bonus Challenge and re-enter it by tapping on the same Gym which the Raid Boss was defeated at, but as long as the Raid still occurs on that Gym.

Trainer can capture Pokémon after defeating Raid Boss in the Raid Battle which has ended and is no longer visible on Gym but once they leave the encounter screen they cannot return to it.

History

 * August, 2020 - Raids got Tier 2 merged with Tier 1 and Tier 4 merged with Tier 3.
 * June, 2017 - Raids were open being available for players level 35 and above.
 * June, 2017 - Raids were made available for players level 31 and above.
 * June, 2017 - Raids were made available for players level 28 and above.
 * June, 2017 - Raids were made available for players level 25 and above.
 * June, 2017 - Raids were made available for players level 20 and above.
 * July, 2017 - Raids were made available for players level 5 and above.

Trivia

 * Before introduction of Research tasks and Trainer Battles, Rare Candy, Golden Razz Berry and TMs were exclusively available as rewards from Raid Battles.
 * Originally, the amount of Stardust given per Raid Battle was 500. It was increased to 750 on October, 2018. Then it was increased to 1000 on January , 2019.
 * Legendary Raid Bosses have a base capture rate of 2%.
 * The Raid Boss icon is based off of Rhydon's face — who was the first Pokémon designed and programmed into the original game. There are also various Rhydon statutes that can be found throughout the game as well.
 * On November, 2017, the Raid Bosses were rotated for the first time.
 * During Pokémon GO Park and Pokémon GO Stadium event in Yokohama, for the first time in game, there were several event-exclusive Raid Boss Pokémon available.
 * Pokémon such as Meowth, Pikachu, Wobbuffet, Ursaring, Houndoom and few others were available as Raid Bosses on 4th Tier level.
 * Before January, 2019, the stamina of Tier 3 to 6 Raid Bosses were 3,000, 7,500, 12,500 and 18,750 respectively.
 * Mewtwo in normal Raid Battle and Darkrai in Halloween 2019 are the only Tier 6 Raid Bosses, with buffed HP and CP. They are labelled as Tier 5 in the game and give the same awards upon victory.