The invasion of new species creates an addition to the map!
If you are Lord/Lady and have at least 25 million points, travel to the Harbor and order the Icebreaker License. After paying him 145,000 gold and waiting an hour, you will find a newly added map area called the Slushy Shoreline. Not surprisingly, these mice are all Hydro-type mice, hence the name and location. There are six mice in this location, which drop war supplies and war scraps, but only for a week!
Furthermore, you may have heard a few days ago of a Wolfskie mouse running loose, which can be found in the areas listed below.
Great Gnarled Tree
S.S. Huntington II
Town of Digby
Town of Gnawnia