Raid Battle

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

Background
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, all Pokémon assigned to the Gym will return to their owners, and 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 is an invitation-only. A trainer will receive a notification along with with time, date and location; along with an Exclusive Raid Pass to gain entry into the Raid.

They seem to only run between 6:00AM (starting time) and 9:00PM local time.

Raid Pass
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 Raid Pass may also be purchased from the in-game Shop.

Raid Boss
Upon using a Raid Pass to join the battle, the Trainer and up to 20 other Trainers work together to defeat the Raid Boss. If a Raid Boss is successfully defeated within the five-minute time limit, those Trainers have the chance to catch an extra powerful Pokémon of their own.

Rewards
After defeating a Raid Boss, Trainers receive a collection of rewards, including some new items obtained only by defeating a Raid Boss: Rare Candies, Golden Razz Berries, and Technical Machines.

History

 * 23rd June - Raids were open being available for players level 35 and above
 * 23rd June - Raids were made available for players level 31 and above
 * 23rd June - Raids were made available for players level 28 and above
 * 24th June - Raids were made available for players level 25 and above
 * 26th June - Raids were made available for players level 20 and above
 * 1st July - Raids were made available for players level 5 and above