_Book XX._ The gods, assembled on Mount Olympus, are told by Jupiter that, whereas he intends merely to witness the fight, they may all take part in it, provided they remember Achilles is to reap the main honors of the day. Hearing this, the gods dart off to side with Troy and Greece, as their inclinations prompt, and thus take an active part in the battle, for which Jupiter gives the signal by launching a thunder-bolt. Not only do the gods fight against each other on this day, but use all their efforts to second their favorites in every way. Before long, however, it becomes so evident they are merely delaying the inevitable issue, that they agree to withdraw from the field, leaving mortals to settle the matter themselves. There are vivid descriptions of sundry encounters, including one between Achilles and Aeneas, wherein both heroes indulge in boastful speeches before coming to blows. At one time, when Aeneas is about to get the worst of it, the gods, knowing he is reserved for greater things, snatch him from the battle-field and convey him to a place of safety. Thus miraculously deprived of his antagonist, Achilles resumes his quest for Hector, who has hitherto been avoiding him, but who, seeing one of his brothers fall beneath the Greek's blows, meets him bravely. But, as the moment of Hector's death has not yet come, the gods separate these two fighters, although their hatred is such that, whenever they catch a glimpse of each other, they rush forward to renew the fight. _Book XXI._ Fleeing before the Greeks, the Trojans reach the Xanthus River, into which Achilles plunges after them, and where, after killing hosts of victims, he secures a dozen prisoners to sacrifice on his friend's tomb. Hearing Achilles refuse mercy to a young Trojan, and enraged because he has choked his bed with corpses, the River God suddenly rises to chide him, but Achilles is now in so defiant a mood that he is ready to fight even the gods themselves. In spite of his courage he would, however, have been drowned, had not Neptune and Minerva come to his rescue, fighting the waters with fire, and assuring him Hector will soon lie lifeless at his feet. He ceased; wide conflagration blazing round; The bubbled waters yield a hissing sound. As when the flames beneath a cauldron rise, To melt the fat of some rich sacrifice, Amid the fierce embrace of circling fires The waters foam, the heavy smoke aspires: So boils the imprison'd flood, forbid to flow, And choked with vapors feels his bottom glow. The course of this day's fighting is anxiously watched by old King Priam from the top of the Trojan ramparts, and, when he sees Achilles' forces pursuing his fleeing army across the plain, he orders the gates opened to admit the fugitives, and quickly closed again so the foe cannot enter too. To facilitate this move, Apollo assumes the guise of Hector and decoys Achilles away from the gates until the bulk of the Trojan army is safe.