This is a ingame event series that offer lots of prizes and rewards to players during its 15 days!
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Here is the complete event list:
Decathlon 1: Alchemy
Decathlon 2: Phantom Sealed* using three packs each of Innistrad: Midnight Hunt and Innistrad: Crimson Vow
December 21–23
Decathlon 3: Innistrad: Crimson Vow Traditional Phantom Draft* (Best-of-Three)
Decathlon 4: New Player Decks
December 24–26
Decathlon 5: Zendikar Rising Phantom Bot Draft*
Decathlon 6: Historic Artisan (banned list)
December 27–29
Decathlon 7: Historic (banned list)
Decathlon 8: Singleton
December 30–January 1
Decathlon 9: Traditional Standard (Best-of-Three) (banned list)
Decathlon 10: Strixhaven: School of Mages Phantom Turbo Draft* (a bot draft with each player receiving an emblem with the text "All spells cost [5] less to cast.")
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Everyone who enters an event will receive the Arena Decathlet sleeve!
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If you obtain an outstanding performance in the Decathlon Finals, you will receive Jayce, the Mind Sculptor as an avatar!
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Each event costs 2.000 gold or 400 gems to enter
The structure is:
Best-of-One matches: Play until 7 wins or 3 losses
Best-of-Three matches: Play until 5 wins or 2 losses
To enter the finals, you will need at least 3 Decathlon Tokens
If you obtain 7 wins during the finals, you will receive:
-1 Complete set of Kamigawa: Neon Dynasty
-Jace, the Mind Sculptor avatar
-4 Mythic rare wildcards
-Gold Medal sleeve
-3 Player Draft tokens
-5 Unhinged basic lands
-4 Rare wildcards
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There are also smaller rewards for those who win at least one game during the finals
You will need at least 6 wins to receive Jayce's avatar, though