(Thanks to MiniEmerald, Thanhhieu02, @absol__utely (twitter) and @nt_somewhere (twitter) for this datamine)

Starts on: May 13th 2020, 06:00 UTC
Ends on: 31th 2020, 06:00 UTC

Two stages, one attempt per day.
Opponents field: Blissey, Blissey. Blissey.
 
Stage 1: Challenge Pasio's Trainers
- Power Needed: 4,200
First-time Rewards
- 10 gems
 
Stage 2: Challenge Pasio's Trainers
- Power Needed: 4,200
 
 First-time Rewards
- 10 gems
- 10x Bliss Ticket
(^ last day stage)

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Missions and rewards:
 
Mission 1 | Complete the designated area
x5 Lucky Scroll

Mission 2 | Complete the designated area
x1 1★ Crunchy Lucky Cookie
x1 1★ Creamy Lucky Cookie
x1 1★ Crispy Lucky Cookie

Mission 3 | Complete the designated area
x1 2★ Crunchy Lucky Cookie
x1 2★ Creamy Lucky Cookie
x1 2★ Crispy Lucky Cookie

Mission 4 | Complete the designated area
x5 Lucky Scroll

Mission 5 | Complete the designated area
x1 2★ Crunchy Lucky Cookie
x1 2★ Creamy Lucky Cookie
x1 2★ Crispy Lucky Cookie
Mission 6 | Complete the designated area
x5 Lucky Scroll

Mission 7 | Complete the designated area
x1 2★ Crunchy Lucky Cookie
x1 2★ Creamy Lucky Cookie
x1 2★ Crispy Lucky Cookie

Mission 8 | Complete the designated area
x10 Lucky Scroll
 
Reward for completing all missions: 300 gems.
 
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Battle Rewards:

100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
100%: Happy Ticket (x1) [65%], Joy Ticket (x1) [25%], Bliss Ticket (x1) [10%]
1%: Lucky Scroll (x10)

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Exchange in the shop (tickets):
 
Exchange max 10 times:
x1 Bliss Ticket -> x10 Lucky Scroll
 
Unlimited exchange:
x1 Bliss Ticket -> x50 Co-op Orb
x1 Bliss Ticket -> x1 3★ Crunchy Lucky Cookie
x1 Bliss Ticket -> x1 3★ Creamy Lucky Cookie
x1 Bliss Ticket -> x1 3★ Crispy Lucky Cookie
x1 Joy Ticket -> x1 2★ Crunchy Lucky Cookie
x1 Joy Ticket -> x1 2★ Creamy Lucky Cookie
x1 Joy Ticket -> x1 2★ Crispy Lucky Cookie
x1 Happy Ticket -> x1 1★ Crunchy Lucky Cookie
x1 Happy Ticket -> x1 1★ Creamy Lucky Cookie
x1 Happy Ticket -> x1 1★ Crispy Lucky Cookie
x1 Happy Ticket -> x3 3★ Level-Up Manual
 
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@nt_somewhere's tweet with an image from the event rewards: https://twitter.com/nt_somewhere/status/1260157380706197506?s=20