This is a great idea. I really like the idea of a doorway that you can get lost in and the description of passing through it is imaginative and gripping. How do you make one of these gates or who made these gates? Where can you find them and can they only exist at freezing temperatures? Are they created in place or movable? Also, I would love to hear more about this dungeon.
Great, functional transportation item. I wonder, though, if the ruby heart is magically stuck to the door, how does the user retrieve it? After closing the door, the heart could be thousands of miles away. That might make for some interesting twistiness.
I'm enamored of the first sentence. "The Ruby Heart is the fastest way to get home," is perfectly succicinct, and has that folksy fairy-tale ring to it that I love.
Could you use a similiar supernatural technology or technique to make slippers?
I think you could/should cut some words out of the first four sentences and then describe what happens when the magic is employed in a little more detail.
Does the silver heart burning out mean you only use it once? Does the enchanted distant door look like the ruby door, how many people can pass through it, how long can it stay open and what can you see through the open door? If the magic isn't too obvious: clever players would trick people into passing through it or drop ex-wvies or monsters into the rooms of the unpopular or evil.