Spells are magical events that are brought about by mages using magical gems or blood slaves as fuel. Magic ranges from spells that simply fling a collection of rocks at an enemy, to ones that can plunge the world into darkness, or birth a second sun, or open a gate to the underworld to call forth a decaying god.
Spells are divided into 7 schools, each of 10 levels. These schools must be researched by mages stationed in provinces with a laboratory for the spells to become available to cast, except for level 0 and Holy spells. Each spell has a number of costs associated with it; the caster must have sufficient levels in the correct magic paths; if casting a combat spell they must have the required gems in their inventory; they cannot cast when unconscious, and any conditions such as "cannot be cast underwater" must be met.
For a list of spells, their requisite paths and costs, go to http://larzm42.github.io/dom4inspector/
Spells are researched by putting a mage in a lab and telling him to "research". Each mage adds to your research score each turn, by an amount determined by his paths, your magic scales, and a few Special Abilities. Research is divided, according to the player's choice using sliders, between schools. The schools are:
And an unresearchable school,
Besides the schools in which they're researched, spells are also divided into Paths which determine which mages can cast them.