Modern Horizons contains 254 cards (5 snow-covered basic lands, 101 commons, 80 uncommons, 53 rares, 15 mythic rares), and includes randomly inserted premium versions of all these cards. In addition, there is a Buy-a-Box card numbered #255/254. This set introduced new cards into Modern without them ever being legal in Standard. It contains 209 new cards and (excepting the snow basics) only reprints which previously weren't legal in Modern. For this, it was rigorously playtested by Play Design. The Buy-a-Box card is also a new-to-Modern reprint. The powerful new card options, some with old mechanics, are mixed with flavorful updates for favorite characters. The snow-covered basic lands appear in the land slot of Modern Horizons boosters.