Answer:
I have a tongue, but do not talk. I follow close, but neither run nor walk. Coupled and hitched, but never married. You couldn't bear the load I've carried.
A shimmering field that reaches far. Yet it has no tracks, And is crossed without paths.
What lies in a tunnel of darkness. That can only attack when pulled back?
I have rivers without water. Forests without trees. Mountains without rocks. Towns without houses.
What goes in, but never through? I've got some and so do you. We might lend one, or even two, but only if our trust is true.
The warmer I am the fresher I am.