I finally did it. Made my first public thing on itch. My dumb idea for a bronze age visit from Santa that I had as soon as I heard of this jam. Here's a description of the titular "Grandfather Frost" that I hope will work for your encyclopedia.
The so-called, Grandfather Frost arrives only on the coldest night of the dark season. A towering figure, robed in furs and hidden behind a wooden mask of a bearded face. They ride an elk-drawn sleigh, laden with gifts.
Are they a spirit, a god, or simply the bearer of the mask? Witnesses disagree but I know! I have seen those eyes before, heard that voice. I can’t remember who they were before of course but that must be part of the magic of the mask… Regardless, heed my warnings! Accept their generosity and do not let your own generosity be lacking or a curse shall be upon you and yours.
Who knows, perhaps you too will wear the mask one dark season and be forgotten like, like old what’s their name… no no, wait , it’ll come to me…