According to official post on MTG Arena forums, challenging your friends (or your friendly competition) works like this:
- From the Home Menu, select the “Direct Challenge” button next to the Settings Cog Wheel.
- From there, the Play Blade will open and you will have the option to select your deck and enter your opponent’s username. You’ll also have a clickable version of your username that will copy the data to your clipboard when clicked, so you can easily send over you username with the necessary numerical digits to your friend.
- Select “Play”, and you’ll be taken to a match loading screen while you wait for your opponent to do the same.
- Once you have both challenged each other, the match will begin!
- Rematches are easy as your last opponent will stay entered, and your last several opponents will be saved in a drop-down.
Your House, Your Rules, Mostly
Another fun thing about this feature is that there are very few restrictions to what format you wish to play, as the only deck requirements Direct Challenge enforces are a 60-card minimum and that you have the cards in your Collection. This means you can bring your Singleton deck, or your Standard deck, or (if we have them down the line) cards that may otherwise be banned in a format. Be warned, this means it operates under an ‘honor’ system. If you both agree to play Pauper and your friend tries to hit you with a Turn 3 Gigantosaurus, the system won’t stop them.
Other important things to keep in mind:
- All Direct Challenge matches are “Best of One”. If you want to challenge your friend to a Best of Three, you will have to re-queue once the match completes with a sideboarded deck you’ve edited in the Deck Builder.
- Direct Challenge matches have no impact on your Player Rank.
- Direct Challenge matches will not progress any Daily Quests or Weekly Win rewards.
- We have currently disabled all Timers for these matches (though you can still time out from the server if no actions are taken for an extended period of time.
Additional Social Features Coming Later
The next logical step to this system is a comprehensive “Friend’s List” feature, which will include everything you’ve come to expect from a friend’s list – the ability to add players to it, to see when their online, whether or not their in a match, and the ability to challenge them from the list.