The Ark of Nervilein
Throughout the land there are points where mana concentrates, this are sites of incredible power, where magic reaches new heights of power.
Dubbed Arcane Wells, they follow an invisible flow, always constant but never predictable, while at times the power can flow with the power of a raging current, it could just as easily flow with the power of a dying stream trickle. The duration of this flows also fluctuates, sometimes the flow could last months, even years, and sometimes no more than a couple of weeks.
The places with the strongest and most reliable flow are the places where cities and kingdoms are built on.
Throughout history Arcane Wells have become the single most precious piece of property in existance, owning and controling the flow of Wells is what ensures the prosperity and power of Kingdoms, even the individual cities inside a Kingdom prosper in accordance to this principle.