Simplify the following text for a Grade 11 native English-speaking person.
Original: Luke stabs himself at his mortal point ( under his left armpit ) as Kronos struggles to reassert control , becoming the hero of the prophecy and ending the war on the dawn of Percy 's 16th birthday .
Simplified: Luke commits suicide by stabbing himself in his mortal point when Kronos takes over his body , becoming the hero of the prophecy and ending the war on Percy 's 16th birthday .