Solzati are crystals that Tanar'ri use to trap and store souls. They are often called soul crystals.
A newly created solzati looks like a raw, uncut lump of clear crystal and are generally the size of an apple. If left with no soul in it, the solzati will remain in this form. Once a solzati has a soul inside it will slowly shape itself into a cut crystal. Some owners of a solzati further change it's shape to that of a round ball.
A solzati with no soul inside is cold to the touch, and often gives a feeling of being empty. A being with a soul who touches or holds one, often gets the feeling that they are falling into the solzati. A Solzati with a soul inside it will feel quite warm to the touch, depending on the strength of the soul within. An extremely strong soul can make the solzati so hot to the touch that it can burn.
A solzati can safely hold a mortal soul. A empty solzati is little more then a normal lump of crystal, but a solzati has the strength and durability of iron. As long as a solxati is not physically destroyed it can hold a soul forever. A single solzati can hold only a single soul.