From the announcement:
In its quest for galactic domination, the Empire will inevitably encounter planets with less than ideal conditions. When a mere threat isn’t enough, specialized troops are needed to bring these planets to heel. Imperial troops ready for any conditions are now ready to join your Star Wars™: Legion army.
The Snowtroopers Unit Expansion is now available, and you can add new recruits to your army and unlock new strategies in the battle for the Star Wars galaxy today!