Obsidian Mirrors
Mirrors, in general, have been used throughout history spanning over many cultures. Notably, mirrors have folklore associated with them. Think of how the evil queen in Snow White used her mirror to determine who was the fairest of them all.. or Alice and the adventures of Wonderland and how she steps through her mirror into a fantasy world, and then there's Beauty and the Beast where a mirror was left behind by the old wizard which is referenced as a gateway to the outside world. Mirrors capture very mystical feelings when they are gazed into. Obsidian Mirrors are used as a divination tool and in some cultures the belief is the mirror can actually capture your soul in image. Additionally, we have all heard if a mirror breaks in your possession, you can have seven years bad luck. Perhaps that is due to there being some truth that a mirror captures your soul... when the mirror shatters, it has shattered your own self. Just thinking in theory here.
Mirrors generally are used to reflect how the world is around you. Obsidian mirrors (or "black" mirrors) are said to not reflect the world around you but reflect what is inside. Obsidian mirrors are used today for scrying as a portal of such to reflect into yourself and also your spiritual realms. Scrying with an Obsidian Mirror can help you connect to your inner spirit, astral travel or projection, receive messages from your higher self, meditation, also to access Akashic records, or what is known as the Book of Life which is said to contain every thought and event, and again, as a divination tool to get answers and visions about the future as well as a communicator between yourself and the spirit world. The history of mirrors is centuries old and definitely contains not only an interesting perspective on such tools and our pasts, but a vast wealth of knowledge that can make you go hmm! I personally love the hmm moments as it offers such a beautiful pathway of exploration.
Just to note, these are not a toy. As a seer myself who has a very solid foundation of mirrors in this life and past, I wholeheartedly discourage (just don't do it) anyone from using such a tool for any negativity towards self and/or others. These should be used for self discovery, self work, expansion, and to advance spirituality.