Working on the spell Casting for Legends of Terrestria, specifically the mechanics, converting lore into game mechanics.

Lore Reference: Spell Casting, Disciple Illumine calls upon their deity to grant them power through ritual. These rituals can be as simple as incantation as the Casters of the StarBorn, or as brutal as the Maazetec blood sacrifice depending on the culture and religion. Calling upon the Ethereal being(s) to feed the caster energy from the Mixers, this energy is manipulated by the caster to manifest spells that will reflect their culture and faith. The act of doing this generates heat, respective of the energy drawn to the Illumine. This heat can kill the caster if they push themselves beyond their limit. Certain materials and items can be used to vent or transfer this heat byproduct into, to allow the caster to go beyond their own abilities. The heavier the fabrics/armor the greater the heat build-up, casting in colder environments has a minor positive effect whereas warmer makes casting difficult. As the caster begins to draw this energy, the more heat/energy they build up the more powerful spells they can cast. On the flip side, casting these more powerful spells can be more taxing causing great fatigue. Making repeated casting of these more complex spells impossible without cooling down and casting lower-tier spells. While spells themselves require the caster to understand the fundamental principles of what it is they wish to achieve or make manifest. For instance, if Aia is healing a severed arm, she cannot re-attach the arm. The anatomical understanding she possesses (and Terrestrians as a whole) is limited. Mending wounds must be done with great care, as one wrong move could mend an artery shut. Some items crafted using rare materials “Star Steel” can create weapons, armor that can channel spells and help with heat dispersion. 
 
Heat Levels, Boostable spells, Tiered Spells, and Cooldown timers, special rare items that can amplify casting, and help with heat dispersion. Armor affecting casting/heat levels.

No Mana pools, I found those to be boring.