Oko, Thief of Crowns, Mycosynth Lattice, and Mox Opal are now banned in the Modern format of Magic: The Gathering (MtG). As announced on the Jan. 13, Banned and Restricted Announcement blog post by Wizards of the Coast, the ban is effective immediately in competitive play, and on Jan. 14 in Magic Online.
Oko, Creator of Elks
The card 'Oko, Thief of Crowns' from MtG's latest expansion Thrones of Eldraine, has been the subject of bans in other formats prior to this. The card's dominance in tournament play led to it becoming banned in both Standard and Brawl formats. Standard and Modern formats are currently the most widely-played formats in MtG.
The card, which depicts a fey planeswalker (powerful beings in the MtG universe that could use magic and bend the rules of reality) named Oko is deemed too powerful in constructed formats. One of its abilities allow it to turn any artifact or creature card into a powerless elk.
Oko's ability to render threatening cards useless, along with its ability to create food tokens (cards that could give the player extra life points in exchange for mana), makes it very imbalanced, leading to the ban.
Death to Artifacts
Mox Opal allows players to do explosive combos seemingly out of nowhere, ending games abruptly. Although Mox Opal has been part of strong decks in the past, it only received banning now with its interactions with the card 'Urza, Lord High Artificer'.
Mycosynth Lattice, on the other hand, effectively locks out the opponent from doing anything as long as it's onboard with the card Karn, the Great Creator. The one-two combo gives very small room for opponents to react in time.
The two cards also affect a wider range of decks in Modern, most especially Affinity decks. Affinity decks make use of powerful artifacts to accelerate their mana generation, allowing players to cast strong spells early into the game.
Possible Bans In Pioneer
The Pioneer format, the newest format in competitive Magic that only allows cards released from the 'Return to Ravnica' expansion to be played, is still in its honeymoon period. Launched just last October, Wizards of the Coast is still monitoring the performance of cards and decks right now, and are thus not yet giving bans and restrictions on any cards in the format.
However, the community is currently up with their pitchforks against Walking Ballista, a card that allows it to trade its power and toughness for damage. An upcoming card in the new expansion Theros: Beyond Death' called Heliod, Sun-Crowned that could give the Walking Ballista infinite charges for infinite damage.
Wizards of the Coast has recognized this concern but are choosing not to take any preemptive action against the potential game-breaking combo. They say that they will have to wait for the results of upcoming professional tournaments before making any changes, and see if the metagame would require such a ban.