It's the custom map from the omega supporter pack that has a foiled unique. The player picks the map, map mods, and foiled unique at the end. You won't accidentally do it.
There's a map rarity thing on the bottom telling you how likely your special map is to drop from the pool, and the harder the mods the more common the drop. The "hardcore" option adds 1000% more common. Most mods are like 100-200% more common. Some of the mods are near game breaking like "players and minions deal 10% LESS damage per EQUIPPED ITEM".
Nuts stuff.