The Mirror of Kalandra is used for creating an exact duplicate of a non-unique item. When a player uses a Mirror of Kalandra on an item, it creates a mirrored copy with identical modifiers, sockets, and links. This allows players to obtain a perfect duplicate of their most valuable and powerful items.

Due to its incredible rarity and the unique ability it offers, the Mirror of Kalandra holds immense value in the game's economy. It is often used as a form of high-value currency for trading and acquiring other valuable items.

Obtaining a Mirror of Kalandra is an extremely difficult task, as it is an exceptionally rare drop. It can occasionally be obtained by slaying very powerful bosses, opening certain chests, or through other rare and difficult means. Players often dedicate significant time and effort to acquiring this elusive item.

In summary, the Mirror of Kalandra is an incredibly rare and valuable currency item in Path of Exile. It allows players to create an exact duplicate of a non-unique item, making it highly sought after for its unique ability. Its scarcity and desirability make it a prized possession in the game's economy.