Yes, making proxies is legal, so long as you don't try to sell them
Sure, they might be able to put them back into a players hand from the battlefield or turn them into Islands, but mono-blue card effects just didnt let you search your deck for them, let alone place them on the battlefield
Make sure to check out our guide to the MTG release schedule so you know exactly when these cards will be available, and what's coming up next!

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To top things off, there are also codes included to add each deck into Magic: the Gathering Arena , with an extra code a handy way to get a friend involved online