Short answers, pulled from the story.
Memnon was the king of Aethiopia and son of Eos, the goddess of dawn. He was born to Tithonus, a mortal man snatched from Troy by the morning light. Ancient poets claimed he was raised by the Hesperides on the coast of Oceanus.
Achilles stabbed Memnon through the heart with a spear while both warriors wore divine armor made by Hephaestus. Zeus used golden scales to decide which hero would die, and his entire army fled in terror at the sight of their leader falling. Gods collected every drop of blood that fell from him to form a huge river.
Zeus granted immortality as a final wish from his grieving mother Eos so she could see him alive every day when she opened the doors of heaven. The Aethopians who stayed close to bury their leader were turned into birds called Memnonides. These creatures stay by his tomb to remove dust that gathers upon it forever.
Two massive stone statues stood three thousand four hundred years old in Luxor and were twin figures of Pharaoh Amenhotep III located in Egypt. Greeks and Romans visitors associated these monuments with mythical Memnon since at least the first century. One statue faced sunrise on the winter solstice and linked the colossus to the dawn goddess Eos.
Pliny the Elder recorded that one statue made a sound at morning time that could best be likened to that of a harp or lyre when a string had broken. An earthquake in 27 b.c. caused the northernmost colossus to collapse again, and this broken figure began producing an eerie musical sound once more. Early Greek travelers interpreted this as the half-mortal Memnon calling out to his mother.