ahem
My apologies, the quintillican confederacy. Oh, this is a big question. I may just muddle through.

Quintillica
This probably misses you before you go home. Sorry, should have posted earlier.

Tydfal is actually from Chylorissa, which isn't (I think) part of the Quintillican Confederacy at the moment. I believe it has been at other points in its history. The priesthood Tydfal was raised in is viewed as Theocratic by the Choleic Order, but actually considers itself to be worshiping Wisdom and hates the Quintillican Priesthood.

The religion of the Dawn (Quintillican Confederacy plus independent city states) is mostly polytheistic (worshiping the Spirits of Creation as Gods) and is also fairly heterodox (there are different priesthoods that believe different things, and that practice in radically different ways, both within a given city, and also between different cities). The temple of the Quintillican high priesthood is based at the remains of the Seat of the Priest King of Quintillica. From this we can assume that their magic is strongly influenced by the Demiurge, although the Seat of the Priest King of Vestra is not viewed as being Demiurgic (it is, however, considered to be off limits, and is not directly drawn on for magical power).

Quintillican magic is also going to be very heterodox. The confederacy is urban and cosmopolitan, so magical traditions from all over (including lands to the North) will be found there. At least some of the priestly magic is diabolic and theocratic (involving the summoning and possibly binding of (or negotiation with or service to) either Spirits of Creation or lesser spirit eminations of the Demiurge). These spirits might be used for direct effects, or they might be used as a means to gain magical power which could then be manipulated using spells more like Choleic magic.

The Quintillicans are also much more skilled with Astrology than Choleic mages are (due to their greater involvement with navigation and tide prediction). Quintillican priestly magic is also much better at using mass audiences as a source of magical power (large scale ritual magic, something no one in the order besides the Elenoreans has ever been good at), and are also generally better than the Choleics at boundaries and wards.

All of that is pretty flexible. Sarah certainly knows more about the Chylorissan priesthood, but I don't think anyone knows all that much about the Quintillicans.

More about Tyrulean religion
Like Charles said, there is a great deal of religious heterodoxy in this part of the world: the Tyrulean city states are polytheistic and syncretist, and the culture therefore supports a wide range of competing and specific cults. So feel free to make stuff up with wild abandon.

General stuff --

The various religions of the Dawn city states have a strong ecstatic/orgiastic tradition, which I've always imagined is an important component part of how they derive power from mass audience participation in public religious rituals. A number of the priesthoods draw their members from those men who experience ecstatic epiphany in the course of these ceremonies and are thereby led to dedicate themselves to the Temple, usually through self-castration. Eunuch priesthoods are quite common in the region: the higher ranks of the Quintillican Priesthood, for example, are composed exclusively of cut men. The various religions and cults of the area vary tremendously when it comes to the role of women within their hierarchies, though: some of the cults have exclusively female priesthoods.

The Quintillican Priesthood itself holds a great deal of political power, and I imagine that within its ranks there is a tremendous deal of corruption. The upper eschelons of the Priesthood are goetists who maintain their power through binding and bargaining with Spirits of Creation; the Priesthood of the High Temple in the City of Quintillica itself has also learned how to harness the power of the old Theocratic citadel on which it is built, and it uses this power to ensure Quintillican hegemony over the seas. I would point out, though, that your average everyday adherent to the Quintillican religion is not doing anything of the sort, and would surely be most offended at the very idea of "binding" the Spirits of Creation, whom they worship as gods.

The more aristocratic and elite urban magical traditions of the region tend to be both highly mystical and extremely numerologically and linguistically complex -- think Kabbala. They also tend to deal far more directly than the Cholaeics do with the stuff and substance of magic itself -- what in Ars Magica would be termed vim. Their actual practical magical workings tend to involve weaving strands of magical energy into complex mathematical matrices.

In the more rural inland regions, "Twin Cults" are quite popular. These vary widely in their specific theology and practice, but nearly all of them involve the celebration of gender polarity and fertility through the ritual sexual congress of sanctified fraternal twin priests.

Uh. Does that help at all, or just muddy the waters farther?

Western Atheism
Oh, and just for the record, the corresponding belief to "everyone in the Dawn is a diabolist!" held by the people of the Tyrulean cultures is: "Tympanians have no religion -- they're atheists."