Soul-stones are magic many-coloured rocks that can store and project the memories of an individual. The stones are used to preserve history. Soul-stones can also show its memories to people, as seen when Lief touched Doran'sstone. All members of the Auron tribe carry a soul-stone. Soul-stones appear to change hue rapidly, making it impossible to determine what colour they are. However, a soul-stone does not have any colour, and will appear different to each individual.
Doran's journey to Auron
When Doran the Dragonlover made his way through the Pirran Caverns, he taught the Auron tribe how to use fire to light their caverns since their banishment from the island of Auron. In exchange, the Aurons gave him a soul-stone so he could remember his time in the caverns and record all his thoughts and memories.
When Veritas took the breath of Doran, his body disintegrated and left behind a handful of objects, including his soul-stone.
The Sister of the South
Doran's soul-stone was buried along with his other possessions outside of Ava's shop on The Finger. Lief touched the stone while burying it and saw into Doran's memories. This allowed him to summon the remaining dragons to fight the Ak-Baba on Dragon Night.