Entropic Quest, by Tom Lichtenberg and Johnny Lichtenberg
Four people are selected, seemingly at random, by an invisible being who communicates to them through wild animals. They are told they must go somewhere, find something, take it somewhere and do something with it. This is all they know. The thing, whatever it is, could be anything, and it could be anywhere. As for the chosen ones, they have other problems. Two are bitter rivals in an endless and seemingly pointless game, another is a novice, newly torn from her everyday life, while the fourth has been an old man for much too long, for all of them are immortal, exiled with nothing into an infinite forest by a world that cannot tolerate their existence. As they struggle to work together to achieve a goal that none can even imagine, failure might just be their only option.