Characters start with magic by selecting the Wizard Class, or one of the elemental Specialties. Spells each belong to one of the elements, and have a level from one to four. Each character starts with some spells of the levels they can cast, and can find additional spells while adventuring.

There are several types of magic in the world, but only the Touched (the player characters) can draw from the energies of Chaos, with its power and instability. We can talk about the sorts of magic which enemies and allies may use at a later time.
Abilities related to things like becoming invisible, healing party members, or harming undead are independent from spells, and do not count as casting.

[...] With the exception of the Wizard Class, a character with an elemental Specialty has access only to spells of that element. A Wizard with an elemental Specialty is most effective in that element, but still has access to all the others.

On Casting

Spells come in various kinds, damage, zones, buffs, and summons, and the support spells take up less of the character's turn, allowing them to attack as well. Characters can (with a few exceptions) cast only one spell per Turn, even if they've accrued some extra actions.

Casting spells, with the exception of stealthy spells (the province of Nature), makes the caster vulnerable to attacks of opportunity if they are in the threat range of enemies. Casting, with the same caveats, also breaks the invisibility of Shadowmaster.

Characters can cast first and second level spells without cost, so Wizards always have something to do. Third and fourth level spells have a Toll, or mana cost. Channeling that amount of energy just isn't good for the body.

The Casting Toll

During rest, the player can draw down his maximum hit points and transfer them, one for one into mana. During the remainder of the day, if the caster has exhausted his prepared mana, she can burn her maximum hit points down directly at a cost of 2 for 1 mana. Third level spells cost three mana to cast, and fourth level spells cost four mana. Characters can theoretically cast high level spells until their maximum hit points reach 1 hit point. This isn't considered a safe choice.

So, a character with 80 hit points could use the resting ritual to bring his hit points down to 60 and gain 20 mana. These hit points are unavailable during that day. No one can heal the character above 60 hit points. At the next rest, the mana converts back to hit points and the character again has 80 hit points.

Spellcasters

As you can tell, its possible to take any Class and add an elemental Specialty, so potentially every character can cast some spells. It could make an interesting team, but would find some situations challenging. Its a matter of how you want to play, the freedom of choice.
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