“It was said in the old days that every year Thor made a circle around Middle-earth, beating back the enemies of order. Thor got older every year, and the circle occupied by gods and men grew smaller. The wisdom god, Woden, went out to the king of the trolls, got him in an armlock, and demanded to know of him how order might triumph over chaos.
"Give me your left eye," said the king of the trolls, "and I'll tell you."
Without hesitation, Woden gave up his left eye. "Now tell me."
The troll said, "The secret is, Watch with both eyes!”