Ten Feet, Three Eyes, One Tail

Norse tradition liked a riddle-contest with a life riding on it. Hervarar saga stages one: a stranger called Gestumblindi puts riddles to King Heiðrekr, who answers every one. Then comes this. Who are the two that run on ten feet, have three eyes between them, and one tail? The king solves it — the one-eyed rider on the eight-legged horse — and in solving it works out exactly who he has been talking to. The riddle only functions if an audience finds that horse instantly recognisable, which tells us something no poem about him does.