[credits to @absol__utely (twitter) for these]
* This time around, there is no datamine (yet?) for missions (poryphone), so they are not included.
* Legendary Arena rewards are not datamined yet (as of time of making this pastebin), but since the past 2 arenas got the same rewards, I copy-pasted them.
 
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Story Event: Summer Superstars (July 31st)
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Stages:
370x 💎
1x 3★ Support Move Candy
1x 4★ Tech Move Candy
Medals


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Rock-type Egg Event (August 11th)
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Stages:
120x 💎
1x 1★ Egg - Rock-Type Pokemon Egg
1x 2★ Egg - Rock-Type Pokemon Egg
1x 3★ Egg - Rock-Type Pokemon Egg
30x 1★ Berry Tart
10x 2★ Berry Tart
5x 3★ Berry Tart
1x Egg Move Candy

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Legendary Event: New World Dilemma (August 17th)
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Prize Box:
3000x Co-op Sync Orbs
2x 5★ Power-Up
1x 5★ Strike Move Candy

Stages:
270x 💎
1x 3★ Strike Move Candy
1x 4★ Strike Move Candy
Medals


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Legendary Arena - Latios (August 20th)
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Stages:
Part 1:
200x 💎
1x 4★ Power-Up

Part 2:
200x 💎
1x 4★ Power-Up

Part 3:
400x 💎
1x 5★ Power-Up

Missions:
2000x Co-Op Sync Orbs
Medals