NOVA: Mysteries of Sleep Like virtually every other animal, humans need sleep to survive. But why? What do we gain from spending nearly a third of our lives in such a defenseless state? And what's at stake if we sleep poorly? The functions of sleep have long been something of a mystery. But now scientists are peering deep into the brain to see what happens while we snooze. One ...。叙述世上曾经存在着一种被称为“夜行神龙”的生物,他们有着强壮的身体、锐利的爪子和有力的翅膀。白天,他们只是高塔的石像;但当夜晚来临,他们就会活动起来,成为黑夜的守护者。在西元994年的苏格兰城堡,神龙与人类结盟,共同对抗外敌入侵。但之后却因为人类的阴谋,神龙们惨遭灭族。悲伤的神龙领袖带着残余子民,在魔法师的法术下,选择了保持石像状态,陷入永世的长眠。。