This is a lame question, but my troupe wants to get the Latin name of its covenant right. We're naming the covenant "Winter's Breath," but we're not sure whether that ought to be "Hiberna Spiritus" or "Hibernus Spiritus." I'm sure that someone around here knows Latin. â€” which should it be?
Winter, as a noun, is "hiems." To make it possessive, you use the genitive case, which is "hiemis." So, you could say "Winter's Breath" with "Hiemis Spiritus." Alternatively, "Hibernus" is an adjective that means "wintry, like winter." If you want to call the covenant "Wintry Breath," it would be "Hibernus Spiritus," because the adjective "Hibernus" must be the same gender as the noun it modifies, "Spiritus."
The FAQ has a short entry I wrote about figuring out this kind of basic Latin, which you might find useful. It's here: redcap.org/FAQ/FAQ2.html#latin.
There are other words both for 'breath' and for 'wintry', as also Erik Dahl has pointed out above. I don't recommend anima or spiritus for breath, though, since both have already become philosophical terms with different meaning in the middle ages.