Creating a sigl requires an enormous quantity of essentia, and the only place where so much essentia can naturally be found is at a Well.
Despite its name, a Well is not created in the same way as a human-dug water well – a better analogy would be a natural pond or lake. When essentia currents converge, the essentia pools and accumulates, like streams feeding a body of water. The Well continues to ‘fill’ until it reaches its natural capacity, at which point it stabilises.
Wells can be permanent or temporary. Permanent Wells are those fed by stable, well-established currents of essentia, and when tapped, they immediately begin to replenish themselves. This process of replenishment is slow, but consistent, and a skilled drucrafter who takes the time to become familiar with a particular Well can generally predict with a fair degree of accuracy how long it will take to refill. The time for a Well to fully replenish itself varies, but tends to average to about one year.
Permanent Wells can either grow or shrink, depending on how they are treated. A permanent Well that is carefully nurtured can last for centuries, and can even grow in strength, though such growth is unpredictable and slow. By contrast, a Well that is fully and repeatedly drained, and given no time to recover between uses, is likely to weaken or dry up entirely. Unsurprisingly, it’s much easier to harm a permanent Well than it is to nurture one. Growing a Well is the result of years or decades of slow, patient work, while destroying one takes a fraction of that time.
Temporary Wells are a different story. If a permanent Well is a natural pond or lake, a temporary Well is like a giant puddle left by a flood. They accumulate more quickly and more unpredictably than permanent Wells do, and they’re unstable. A permanent Well that’s left untouched will stay filled practically forever; a temporary Well will eventually diminish and drain away to nothing. Taking essentia from one destabilises it, further accelerating this process. Like blooming flowers, or fruits fallen from a tree, temporary Wells have a very short lifespan, and if not used will wither away.
Wells in Europe are classified according to the Faraday scale, which is a measure of how many sigls the Well can sustainably make in a year (this typically means leaving at least 10% of the Well’s essentia untouched). A Well with a Faraday rating of 1 can sustainably produce exactly 1 D-class sigl per year. This is doubled for each half-class above D, as follows:
• A Well with a Faraday rating of 1 can produce 1 D-class sigl per year.
• A Well with a Faraday rating of 2 can produce 1 D+ sigl, or 2 D-class sigls, per year.
• A Well with a Faraday rating of 4 can produce 1 C-class sigl, or 4 D-class sigls, per year.
• A Well with a Faraday rating of 8 can produce 1 C+ sigl, or 8 D-class sigls, per year.
• A Well with a Faraday rating of 16 can produce 1 B-class sigl, or 16 D-class sigls, per year.
. . . and so on. A-class sigls require a Well with a Faraday rating of 64, and S-class sigls a Well with a Faraday rating of 256. Such Wells are very rare: the entire UK contains perhaps twenty Wells capable of producing an S-class sigl, and there are countries in the world with no S-class Wells at all.