Magic is known and accepted across the realms, though its place in society varies. The church and its academies employ magic for divinations and the study of the stars. This sanctioned practice is justified by scripture: to read the heavens is to serve the gods. Within these bounds, magic is lawful and revered.
Outside these halls, magic is rarer. Access requires wealth, a teacher, and years of practice. The common folk may recognize a mage by their strange tools, but few understand how those tools are used.
Magic requires preparation and equipment.
Implements are grafted into the caster, allowing the mage to draw magicka into their body.
Catalysts are tools such as staves, totems, or arcane thimbles, that shape and project the spell.
Offerings may be made to strengthen the casting. Arcane ingredients, such as special flowers, the organ of a monster, or even blood.
Magic places a strain on the body. Common effects include fatigue, nausea, or even bleeding. Prolonged use produces tar, a byproduct of spellcasting. It forms in the blood and sickens the caster. Years of tar exposure cause irreversible mutations.
Common side effects of spellcasting may include growth spurts, growth of additional limbs and organs, deformed teeth, darkened eyes, and other similarly uncanny morphisms.
Most importantly, tar is addictive. Many mages grow dependent on their bodily corruption. Tar's morphisms often reflect the nature of the magic: a fire mage might smell of brimstone, weep sparks from their eyes, or release smoke from their mouth as they speak.
Some workings do not require channeling magicka through the body. Rituals combine ingredients, gestures, and incantations to create an effect. They are powerful but demand time, rare resources, and careful preparation.
"By the stars the world was made. Ears to hear, tongues to speak, and eyes to see were given unto you. Mark the heavens, and in their measure find My will."
Players of Heart & Steel may approach magic in two ways.
Truths represent repeatable, reliable power. As always, a truth's name and description set its scope. Typically they require some form of skill check. For more powerful effects, the GM might require the player to strain that truth, or consume an appropriate supply.
Improvised magical effects are suitable for vocations and heritages that are explicitly magical. If a character commonly uses implements and catalysts, it is not beyond reason that they would be able to create their own spells during play. As always, think of the narrative power the character has. Fire mages might suffer curses on checks made to magically charm people but excel at hurling fireballs.
You still use your Skills when casting. A Truth provides the means, but the Skill defines the method. Command might exert control over fire, Charm might bewitch with enchanted words, and Soothe could be used for healing magic.