The Wizarding World of Harry Potter is full of unique mysteries and unanswered questions, hinting at a deep and mystical history that audiences have never gotten the chance to fully explore. One of the most enduring since its introduction is the Veil hidden within the Ministry of Magic, with its mysterious fabric seemingly serving as a gateway between the worlds of the living and the dead.
But the same fabric in the Veil might have appeared elsewhere in the series as one of Harry's most important tools -- the Invisibility Cloak he's had since the events of Harry Potter and the Sorcerer's Stone.
The Veil remains a unique and enigmatic element in the Wizarding World. Introduced in Harry Potter and the Order of the Phoenix, the Veil was found within the Department of Mysteries. Located deep in the heart of the Ministry of Magic, the Department of Mysteries was dedicated to confidentially researching their world's unique items. This includes the Veil, which author J.K. Rowling once suggested had existed in that place long before the Ministry of Magic formed -- and seemingly based themselves around the Veil.
Found by Harry and his allies during their attempts to escape Death Eaters, they discovered the Veil in the aptly named Death Room. While most of the group could only see the Veil and were largely unaffected by it, Harry and quirky Luna Lovegood were both drawn to the sound of voices emanating from it. Considering these two were the only ones who could see the Thestrals (creatures only seen by those who've witnessed death), this suggests the Veil is indeed connected to the afterlife -- with any who come into contact with the Veil dying instantly.
It's possible, however, that part of the Veil had been present across the course of Harry Potter, and no one realized it. A theory from Reddit user YermanFromOverAlong potentially tied the Veil to Harry's Invisibility Cloak, suggesting they are actually the same material. While other Invisibility Cloaks exist within the universe, Harry Potter and the Deathly Hallows revealed that Harry's cloak was supposedly one of three ancient tools known as the Deathly Hallows, bequeathed to his ancestor by Death itself as part of a bargain.
The legend went that the cloak was cut from Death's own, and that the user is able to evade the sight of even Death itself underneath it. While this myth became famous in the Wizarding World, some (such as Dumbledore) believed it instead to be merely the invention of a gifted wizard, Ignotus Peverell -- Harry's ancestor. However, neither theory was confirmed one way or the other. But the Cloak being able to hide anyone within it could explain why Sirius Black's body wasn't able to be recovered after it fell into the Veil -- disappearing from sight in both the film and book version. In a sense, his body was rendered invisible once and for all.
It's an interesting concept, and one that ties the Veil a little closer to the overarching story of Harry Potter. As just the Veil, the monument serves little actual purpose in the story. But if the fabric of the Veil is indeed the same as the Invisibility Cloak, then it quietly serves to foreshadow his eventual discovery about his own Cloak. It's one of the pieces of Harry Potter lore that has yet to be fully delved into, an aspect that could carry multiple meanings and ramifications if true.