Sorcery is one of the forms of magic in Mundus. It makes use of energy from Leylines and can power extremely large devices and works. It is the magic which suspends Helion in the air and powers much of its infrastructure, and it is the primary profession of the Zoph caste of Karthack.
Sorcery is the most common magic in Dace, by a broad margin. Many believe that this is because of the great amount of Orichalcum mined there, which is known to create sorcerous talent in young populations. The Order of St. Radec near Sarvuna is a fortress monastery that trains Dace's young sorcerers, and most go on to serve in the Order's militant ranks, and act as rangers, peacekeepers and agents of the state in Dace and abroad.
In low concentrations, sorcery is invisible, unless visual cues are added as part of the spell. In higher concentrations, it becomes visible naturally, and is normally associated with pale blue.
That said, most people can actually feel sorcery being used nearby. It's a subtle thing, and if it's constant you can tune it out after a while, but it's very recognizable. Highly trained people can tune this in further and basically interpret what kind of sorcery is happening where, without the use of special tools.
Professionals can acquire magestone lenses, which simply make the strands of sorcerous energy visible when peered through. The Orredin can do this naturally, though it requires a conscious effort to do so, sort of like holding one eye closed.