10 Biggest Unsolved Harry Potter Mysteries

2. The Veil

Within the Department of Mysteries, but also far bigger, more mysterious and, in the context of the series, important is the veil, otherwise known as the Death Chamber.

While it's frequently thought that falling through here is what killed Sirius Black, that's not the case - it was Bellatrix's spell that murdered him, and he was dead as he passed through.

That, however, doesn't make the place any less interesting. Like the other rooms, it's obviously somewhere to study death, but why cannot someone living go through the veil? It doesn't seem to merely be a room of objects like space, time, and thought, but with a deeper, darker magic at work. It appears to work like a gateway of sorts between the living and the dead, but any more than that is unknown.