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Companion Mechanic Update Patch Notes – Core Set 2021 Preorder Now Available

The new patch fixes brings the enforcement of the new ban list and the Companion mechanic change announced on June 1 – read on for the logistics of the change, including Wildcard refunds and how the banned cards are obtained going forward. It also introduces the two updated preorder bundles for the upcoming Core Set 2021 (both planeswalkers revealed on the debut show), as well as some bug fixes.

Core Set 2021 Preorder

Core Set 2021 Preorder

Bans and Companion Rules Update




  • 50x Core Set 2021 boosters
  • 1x Card of Liliana, Waker of the Dead
  • 1x Liliana, Waker of the Dead Card Style
  • Waker of the Dead Sleeve


Core Set 2021 Set Mastery Contents

Base Set Mastery

  • 36x Core Set 2021 booster packs
  • 5x Core Set 2021 Mastery Orbs

Set Mastery Pass


Cards and Boosters

  • 20 booster packs (x5 ELD, x5 THB, x5 IKO, x5 M21)
  • 10 mythic rare Individual Card Rewards (ICRs)
  • Level 91 and Beyond: Uncommon ICR (1:20 Upgrade Rate)


  • Best Friend Basic Sleeve
  • 15 common Card Styles
  • 10 uncommon Card Styles
  • 25 Mastery Orbs (each can be redeemed for card styles on the Core Set 2021 Mastery Tree)
  • 5 Dog-themed Pet Variants
  • Level 85 Ugin Exquisite Sleeve (Exquisite = Card Sleeve with VFX)

Gold and Gems

  • 4,000 Gold
  • 1,200 Gems


  • Player Draft Token (Can be redeemed for a Premier or Traditional Draft)



Once per game, any time you could cast a sorcery (during your main phase when the stack is empty), you can pay 3 generic mana to put your companion from your sideboard into your hand. This is a special action, not an activated ability.


  • Agent of Treachery is banned.
  • Fires of Invention is banned.


  • Agent of Treachery is suspended.
  • Fires of Invention is suspended.


If you were participating in a Traditional Standard, Traditional Historic, Standard Event, and/or Historic Event using a deck that included these cards prior to the June 4 game update, you will still be able to complete the event with your current deck. Please note that your deck will be flagged as invalid because of the ban, however, this will not prevent you from finishing a previously entered event. Once you have finished the current event, you will no longer be able to submit decks that contain these cards.


These card bans and suspensions will immediately go into effect for all Standard and Historic play queues once maintenance on June 4 is complete. This includes Standard Ranked, Traditional Standard Play, Traditional Standard Ranked, Traditional Historic Ranked, and Historic Ranked.


  • Players who have Fires of Invention and/or Agent of Treachery as a part of their in-game collection on MTG Arena prior to the game update on June 4 will receive an equal number of rare Wildcards added to their collection as part of the update.
  • Players can still redeem Wildcards for Fires of Invention and/or Agent of Treachery for play in formats where the card is legal, such as Brawl or friendly Direct Challenge matches. There will be an additional confirmation messaging when crafting these cards to remind players that these cards are currently banned in Standard.
  • Players will not be receiving Wildcards as a result of the companion rules change, as these cards are still playable in both Standard and Historic.
  • We will be adjusting the Throne of Eldraine and Core Set 2020 pack collation to change the rate in which Fires of Invention and Agent of Treachery appear in booster packs. After the June 4 game update, players will only receive copies of these cards if they have collected playsets of every other Standard-legal rare card available in the respective boosters.
    • These changes will not impact the collation of cards in Limited boosters used in Throne of Eldraine or Core Set 2020 Sealed and Draft events (cards will still appear at their original distribution rate).
    • There are no changes to pack collation as part of the companion rules change.
  • Fires of Invention and Agent of Treachery will be removed from Standard ICRs. As a note, these cards are currently not available as Historic ICRs.


  • Logs now contain more pack information when drafting. An example Output Log is available below.


  • Profiles once again show the remaining time in the current Ranked season.
  • The “Mastermind” emblem is no longer craftable.
  • The game client should no longer consider a 16-card sideboard valid (Note: This was typically a result of companion shenanigans, however the deck would fail server validation when attempting to enter a match).
  • Players should no longer experience a brief delay during the Victory/Defeat screen
  • The “intention line” should now properly follow the cursor on all battlefields.
  • Godzilla Monster Series card styles should no longer cause clipping issues when deckbuilding in the horizontal view.
  • Permanents that changed control no longer flip around attack.
  • Puppet Jace’s sound effect should no longer continue playing after the animation has stopped playing.


Source: JUN 5 – Patch Notes

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