What was the horror at the Xanthus river?

Answer 1

In Book 21 of The Illiad Achilles singlehandedly splits the Trojan army, driving half back into the city and half into the river where he begins hacking them to pieces with no mercy. The river god Xanthus complains to Achilles that all the corpses are impeding the flow of the water and asks him to stop killing the Trjans. Achilles agrees, but then says he first has to kill the remaining Trojans. At this point Xanthus attacks Achilles, throwing the corpses of the dead out of the river and sending large waves to drown him. Fearing he'll die without honor, drowned like a child, Achilles prays to Zeus for assistance. Athena and Poseidon hear and promise Achilles he won't be killed and tell him to kill the Trojans and Hector. Athena gives Achilles speed so he can outrun the waves and Hera calls on Hephaestus, the god of fire, to fight Xanthus. Hephaestus sets the corpses on fire and all the plants near the river are burned as well, the river boils and all the animals in it die, finally Xanthus concedes the battle.