|This article is about those with extremely magical abilities. For the quest in The Witcher, see The Source.|
A Source is a person born with a natural affinity for magical abilities which are rather difficult to control once they have bloomed, which can sometimes lead to mental illness, like catatonia, if not helped.
Schools of sorcery, like Aretuza and the facility in Ban Ard, were created to help these children cultivate and control their powers, lest the abilities drive them mad. At one point, if one learned of a Source, mages from these schools would hunt them down and tear them away from their families by force or deceit. However, this practice eventually died out by the 1260s and was replaced with a softer approach: any mage that learned of a Source was required to inform the Chapter of Wizards so they could keep an eye on the Source and, at the right time, try to fascinate them with magic to bring them into the fold.
Stressful situations usually work as the trigger a Source's ability. However, this is double-sided: while Sources can wield an extreme amount of power, it's completely uncontrollable and will only happen when they least expect it as they act more like a transmitter of magical energy, rather than wielders of it. This can lead to dire situations where even a castle or half a town can be destroyed if not brought under control.