A Stranger is a person who can control an element or special aspect.
At first the Stranger needs their corresponding stone then it has to accept them. For that they need to prove that they have a certain requirement such as "bravery" or "kindness". Once they have proven themselves, the stone turns into a stick, which is the new weapon of the Stranger and helps them control their element. The Stranger also needs a saying he invents himself (for example: "Sakataki Crystal Sword") for an attack.