DeNA has announced that the Legendary Arena Regirock will take place from June 24th, 2021 at 11:00 p.m. until July 8th, 2021 at 10:59 p.m.

Legendary Arena Regirock

Legendary Arena: Regirock is back! Starting today, Legendary Arena: Regirock returns! New Event Missions have been added along with its return! You can complete higher difficulty missions to get Gems!

Date/Time

June 24, 2021 at 11:00 p.m. - July 8, 2021 at 10:59 p.m.

Legendary Arena

The Legendary Arena is a special battle area where you can form multiple teams and take on the challenge using a set number of sync pairs. You can complete the related missions to earn Medals that can only be obtained here!

Important

• To attempt Legendary Arena missions, you must have completed Main Story Chapter 2: Defeat Team Break! (Normal) in single-player.
• Your area info and mission completion data will be saved at the event’s conclusion and will be used the next time this event returns.
• While Legendary Arena missions will also be displayed on the General missions screen, they cannot be attempted outside of the challenge period.
• The event missions held at the same time as the Legendary Arena do not count toward the completion requirements for Legendary Arena Mission Completion Rewards.
• All completion rewards for event missions held at the same time as the Legendary Arena must be claimed within three days of the mission period ending.
• The time period and featured content are subject to change without notice.

Source: https://pokemonmasters-game.com/en-US/announcements/Event_3050_4W_5

The Next Region for the Champion Stadium

The Next Champion Stadium Challenge. The details for the next Champion Stadium challenge are planned as follows.

Unova Challenge

In the Unova Challenge, you can go up against the Elite Four and Champion of Unova during the time period listed below.
Note: For the duration of the Unova Challenge detailed below, you will not be able to take on Champion Stadium battles for other regions.
Note: Medals for regions that are not currently active will be available during the next challenge that features those regions.

Unova Challenge Date/Time

July 4, 2021 at 11:00 p.m. - August 8, 2021 at 10:59 p.m.

Important

• You can participate in the Champion Stadium after you complete Main Story Chapter 10: A Reason to Battle (Normal) in single-player and collect all PML Badges.
• Medal acquisition and Hall of Fame information will be saved for each region regardless of event date/time.
• Details about the time period and featured region will be included in notifications going forward.
• The time period and featured content are subject to change without notice.

Source: https://pokemonmasters-game.com/en-US/announcements/Update_3050_4W_1