Latchkey
For centuries a barrier held the glacier back from the valley. Shrines kept it, and under each shrine a bound thing slept behind a seal nobody had made. When the barrier failed the seals broke, and the bound things woke. The latchkey is cut from the broken metal of those seals. Each key came from a lock that once held the dark under a province. Now it opens your own door from anywhere. When the new barrier was woven, the priesthoods swore no settler would be lost to the cold again. A homeward blessing is that oath. Turn the key, and a doorway of frost takes you to the hall of your home. Each trip spends one blessing, which you buy at a province shrine. The first trip after the world wakes is free. The key rests an hour between trips, and it will not turn in a fight.
Using it
turn latchkey - go home turn latchkey <place or owner> - choose the door, if it knows several look at latchkey - its blessings, and whether it is ready bless latchkey - at a province shrine: one blessing bless latchkey <count> - at a province shrine: several at once
A homeward blessing costs 10,000 silver at the altar of any restored, consecrated province shrine, in any province. The altar blesses a key up to a hundred times at once. A key bound for a great tower rests half as long between trips.
A mount you ride goes through the frost with you. A mount on a lead cannot follow, so the key will not turn while you lead one. Ride it, or let go of its bridles with lead.
The key forms on your door the first time you walk into the hall of your finished home and stay a few moments; leave too soon and it forms on your next visit. A co-owner's forms the same way; guests carry no key. If you lose yours, kneel at the altar of any province shrine and type bless latchkey: a new key costs the price of one blessing, and it keeps every blessing the old one held.