JK Rowling's Harry Potter foreshadowing is absolutely legendary and her ability to drop tiny breadcrumbs throughout her books is well recognised but did you notice that she dropped a Deathly Hallows CLANGER right in the opening chapters of Harry Potter and The Half Blood Prince?
Xenophilius Lovegood explains what The Hallows are for our heroes in the seventh and final Potter novel, but JK put all three of them - the Elder Wand, the Resurrection Stone and the Cloak of Inivisibility – right under our noses throughout the series.
And in Harry Potter and The Half Blood Prince, she put them all right under our noses at the EXACT. SAME. TIME.
So basically, if Dumbledore had just borrowed Harry's cloak, he could have been the Master of Death.