List of Raid Bosses changes

From the launch of Raid Battle, until now, there were many changes to Raid Boss pool and their tier. Usually, a new Legendary Raid Boss or events update the whole pool in order to match a specific theme.

June 23rd
The launch of Raid Battle included tier 1 to 4 Bosses.

July 22nd
The first Legendary Pokémon Articuno and Lugia were released in tier 5 Raid Battles.

July 31st
Moltres replaced Articuno.

August 7th
Zapdos replaced Moltres.

August 13th
All Legendary Birds along with Lugia were available until the end of the month.

August 14th
Mewtwo was released in EX Raid Battle only.

August 31st
The Legendary Beasts Raikou, Entei and Suicune took place of tier 5 raids. They were exclusive to specific region each month and switched locations at the beginning of each month.

November 4th
Tier 1 to 4 Raid Bosses were updated for the first time.

November 21st
Magikarp returned to Tier 1.

November 27th
Ho-Oh joined the tier 5 raids until December 14.

December 1st
The Legendary Beasts left.

December 8th
The main release of Hoenn Pokémon made Mawile and Absol become the first non-Legendary Pokémon to be raid-exclusive.

December 14th
Ho-Oh left, leaving around a day with no tier 5 raid for the first time.

December 15th
Groudon became available.

December 21st
Wailmer was added to replace Metapod in tier 1 with the release of aquatic Hoenn Pokémon.

January 12th
Kyogre became available along with Groudon.

January 16th
Groudon left.

January 23rd
Aggron was added to replace Victreebel in tier 4 with the release of desert Hoenn Pokémon.

February 9th
The whole raid pool was updated with the release of sky Hoenn Pokémon, releasing Rayquaza and notably reducing amount of Raid Bosses.

February 15th
Kyogre left.

February 23rd
Kyogre and Groudon returned in Legendary Week alongside Rayquaza until March 5th. The following egg and raid pool would depend on which Legendary Pokémon was defeated more in this event.

March 5th
Rayquaza won the Legendary Week event, the raid pool featured some Pokémon that typically preferred windy weather.

March 16th
Lugia returned to Raid Battles with shiny variant available, making it the first Shiny Legendary Pokémon in the game. Mainly the types of tier 1 to 4 Raid Bosses are strong against Lugia.

April 2nd
The Eon Duo was available for the first time. At first, Latias appeared in Asia and Europe while Latios appeared in America and Africa and then they would switch locations on May 8th. Shuppet, Granbull and Houndoom were only available in Latias regions while Duskull, Pinsir and Walrein only appeared in Latios regions. Mainly the types of tier 1 to 4 Raid Bosses are strong against the duo.

April 10th
The Kanto Celebration updated the tier 1 to 4 raid pool to all Kanto Pokémon.

April 18th
Raid Bosses returned to previous layout after the end of Kanto Celebration.

May 1st
The Battle Showdown featured Fighting-type Raid Bosses.

May 15th
After the end of Battle Showdown, Niantic accidentally used the Raid pool of Lugia in March. Later it returned to the Raid pool of Latias and Latios.

May 19th
Ho-Oh returned to Raid Battles with shiny variant available. Its addition did not affect other Raid Bosses.

May 24th
The Adventure Week featured Rock-type Raid Bosses. Region-exclusive Pokémon Lunatone only appeared in Europe, Asia and Australia, and Solrock only appeared in the Americas and Africa, just like their distribution in wild at that time.

June 6th
After the end of Adventure Week and Eon Duo, Raid Bosses returned to previous layout with only Ho-Oh available in Legendary Raid.

June 7th
The Water Festival featured Water-type Raid Bosses, highlighting shiny Kyogre. It is noted that Croconaw was previously a tier 1 Raid Boss, making it the first Pokémon to have tier changed.