Liturgy

"Second Precept: The hunger for transient things is the curse of the ghost, but the contemplation of ideals is the way of the immortal." -Abbot Higarashi of Okuribi Monastery

Ideals hold power beyond that of crude matter.

Where most mages wield the virtues of lightning or speed or blood, virtues of the Empyrean Realm, people of faith connect themselves to the lofty concepts of the Intellectual, or Divine Realm. It is belief in ideals like Justice and Protection and Conquest that grants the clergy power, the ideals that the gods hold dominion over. A priest makes a moral argument; wizards explain how aether should be shaped into a spell, but a cleric explains why it would be in keeping with the ideals they embody for a spell to take shape. To this end, they memorize a body of quotations pertaining to their faith, known generically as the liturgy but specifically as hymns, eddas, sutras, sermons and proverbs.
Priests need the right quotation for the event, but unlike other mages, they also need a spiritual synchronization. To speak a liturgy, one needs two things. The first is philosophical agreement. Any action done in the name of an ideal must agree with the ideal. A worshiper of the god of Fertility cannot call upon that aspect to blight a crop. The second thing is pure conviction. One must believe fully in the purpose of their liturgy, without doubt. If a cleric does not believe fully in their ideals, or does not believe their actions support them, the aether will bleed from the spell.
Despite what many of the faithful will tell you, the gods do not personally decide the outcome of every liturgy. A patron god does not take a blessing away on a whim. However, the will of the deity affects their domain, as do the beliefs of their cult. A liturgy is derived from the traditions of the faith - built on the framework of the god's higher purpose, but shaped by their personality and quirks and formed to fit the lives and needs of the church that follows them. A god with power over weather will have followers whose liturgies concern the winds and storms. If that god is short-tempered, the priests will believe in the righteousness of their anger more than the followers of a gentle god. If that god's cult is in the desert, their liturgies will concern the sandstorms more than the snows. In this way, the magic of a deity differs between sects.
Unlike witches and wizards, who struggle to muster the aether needed for their spellcasting, clerics must take care not to attempt something beyond them. A witch unable to convince the Empyrean she has the power for her spell simply fails. A cleric whose faith is insufficient risks being injured by the power they wield, burned out by the awesome power of an Ideal too large for a mortal soul. Celestials are like incarnations, but they bear ideals in their beings instead of virtues.They can wield liturgies with much less effort than mortals, but being bound to them is limiting. A priest of a god of war can still put down the sword, but an angel of war can only fight. To use holy magic is to weigh your imperfections against something eternal.

Liturgies are primarily used by clerics. When they cast, they must declare aloud the verse they are using, though some with will write spells as wizards do and read them out. Those faithful who do not go through the academic rigor of religious instruction struggle with magic. Most simply pray with the hopes of having their wishes granted indirectly, unable to channel enough aether to do more than hope the gods can hear. Those who apply themselves are in greater danger. A liturgical spell can burn out its chanter, but in some cases, it marks them. Cultivators slowly change their spirits to better resemble incarnations, imbuing magic virtues into their spirits. A miscast liturgy can scar the spirit, leaving it both more like a celestial's, but wounded. People like this often have little choice but to cultivate towards sainthood or abandon magic forever, lest the ideal they have marked themselves with consume them. For this reason, not every member of the clergy learns to cast spells. Some are careful to pray without channeling aether, content to serve the congregation that way.

Prayers that lack the magic of the liturgy are one of the great mysteries of the world. Gods only speak to mortals indirectly; through dreams, visions, omens, and celestial intermediaries. They are vague enough so that their intentions are a matter of interpretation. Mortals must rely on faith, without the hard certainty that the Age of Myths gave them. Rarely, stubborn souls may say the gods do not hear the prayers spoken in their names. The pious might claim instead that the gods send knowledge of the liturgy to answer them.