Desert Survival is a free DLC that introduces a new, more challenging, game mode. In this mode you will have to not only survive the demon onslaught, but also the hardships of the desert. Getting food and water is much harder, scavenge and loot are harder to come by in this desolated area, and only a small portion of your base is fit for planting and farming. To play the Desert Survival challenge, when starting a new game click the "Vanilla" button under the "Game Mode" section, then press the right arrow to select "Desert Survival" instead of Vanilla. Previous saves will not be affected.