In the East the existence of the invisible helpers has always been recognized, though the names given and the characteristics attributed to them naturally vary in different countries; and even in Europe we have had the old Greek stories of the constant interference of the gods in human affairs, and the Roman legend that Castor and Pollux led the legions of the infant republic in the battle of Lake Regillus. Nor did such a conception die out when the classical period ended, for these stories have their legitimate successors in mediaeval tales of saints who appeared at critical moments and turned the fortune of war in favour of the Christian hosts, or of guardian angels who sometimes stepped in and saved a pious traveller from what would otherwise have been certain destruction.