Soulstone

Soulstones are a way to proof your identity and trustworthiness in the desert cultures. Usually people get one when they transition into adulthood. It is a stone that is tied to one's self, however if a person drastically changes due to trauma or other life events, the soulstone might no longer recognise the person, and will not work. In this case the person will need a new one made.
The official soulstones are made by legalised soulstone makers, who are always magic users. They are sealed with an invisible seal, that is unique to each maker, but they are all on a register. You cannot get one of these seals if you are not a legalised soulstone maker. However, because a lot of privilegies are only available for people carrying soulstones, there is a black market for soulstones as well. These stones might work, but might stop working suddenly, and if the person checking your soulstone is skilled enough, they will recognise the lack of a proper seal. Ones that have been discarded as the owner needs a new one are super valuable for black market soulstone makers, because they have the proper seals. That is a reason why old soulstones should never be discarded, and most often if a person needs a new one, they will also continue wearing the old one as a piece of jewellery.
Anyone can purchase a soulstone from a legalised maker if they so wish. They are beautiful stones, worn as jewellery, like rings, bracelets or necklaces. They are a bit costly, so while most people can afford one in their lives, the poorest people probably cannot afford to save enough money for one for their children.
A soulstone is made to order, and many details about a person are taken into careful consideration. Usually getting one involves an interview, and the stone will be ready for collection in about a week, although sometimes it might take longer, if there is complex personal history or peculiar birth circumstances. Most people who are born in a desert city, will be familiar with their local stonemaker from birth, and usually their stone will be ready by the time they participate in the ritual where they become legally adults.