So, you say that you’re interested in building a competitive Modern deck that won’t break your bank account, and you also think you one day might be interested in Legacy? Then have I got a deck for you: mono blue merfolk. Why? Mono blue merfolk is affordable, competitive Modern deck, and it shares about 2/3 of the same cards as its Legacy counterpart. That means that if you build a modern merfolk deck, you’ve practically got a legacy deck as well. What’s more, the cards do not rotate out of either format, so unlike Standard, once you’ve bought and built this deck, you can play it forever.