If Cold Operator is not bugged i.e. working as intended, then I'd find Cultist frickin' difficult to play on huge maps... Because at normal game speed, one of the winters in the first 100 turns gave me -15% health regen on non-allied maps. I spent a lot of turns hiding during winter and war first thing in summer because my neighbours keep killing my converted villages. Once I got Cold Operator skill on my hero, I thought I finally can march an army in winter without suffering from negative health regen - wrong, the only thing that didn't suffer from winter penalties was movement speed...

So the only way to combat that is use Necrophage heroes? That ... sucks.

And yes I know I can garrison my army in a nearby village to pass the winter, but it's pointless if I cannot travel safely into enemy territory and spend a few turns to siege the town without being suicidal.