Based on discussion with community member fishchisel, I've taken a look at Winter's Scythe, and buffed the cold Dark Name somewhat.
-Buffs to most abilities
-Added a catastrophic power which requires you to have already frozen some of the world. Once you've reached a certain point, you can constantly make it colder. The NPCs' only hope at that point is the Lightbringer Ritual.
-Added an ability called 'Blizzard', which allows you to break location-location links, preventing units from travelling between them (amongst other effects). Only works in snowy areas, so you'll have regions of the map where your agents can benefit from weather-based assistance