Preamble
This is version 0.1 of my headcanon/meta fleshing out the organizational structure of the Chantry. It is based off of handwritten notes that I spent a few days writing up while elbows deep in obscure Roman Catholic wiki and encyclopedia articles--so no citations available at the mooment. This is an attempt to give some more meat to the canon information we have for the structure of the southern Chantry in Thedas; I will attempt to point out what is canon information, but it is safe to assume that most of this is not strictly canon. Also, this is very dry, sorry, lmao.
Quick & Dirty IRL Comparison
The Divine (Grand Cleric Exaltant) = the Pope (Bishop of Rome) The Grand Cathedral more or less equals the Vatican.
Grand Cleric = Bishop The Grand Cleric Superior is equivalent to a metropolitan bishop. There's a dozen subtypes of bishop (or archbishop), which are either not needed in Thedas or I have devolved to be equivalent to a Revered Mother in rank. IRL a Cardinal is an entirely separate rank, held in addition to other ranks (e.g. Bishop, Archbishop), and there are at least 60 of them at present. I don't think it is likely there is even 50 (Southern Chantry) Grand Clerics in all of Thedas, and various canon lore sources describe it as being all Grand Clerics who elect the Divine. So, I chose to skip over a direct equivalency for Cardinal.
Revered Mother, Mother = Father Revered Mothers clearly answer to Grand Clerics in the games, and Grand Clerics clearly fill a role equivalent to bishops. IIRC whether there is a distinction between "just" a Mother and a "Revered" Mother is up for interpretation. I chose to interpret it that a Revered Mother is just a Mother+. A pastor in charge of a parish or a title for holding a particular official rank within a curia.
Sister, Brother = Sister, Brother Kind of but not really. Within Roman Catholicism the titles of Sister and Brother are only used by members of religious orders--individuals following specific "Rules" as described above under Third Orders, like Jesuits, Dominicans, etc. Evidence for consecrated life is... messy, in canon. Sisters also seem to be consistently presented as "junior Mothers" or "Mothers-to-be", rather than a separate thing. (IRL Brothers can become priests--Fathers--but you absolutely do NOT have to be a Brother first.) So I added in distinctions between Sisters/Brothers-Dedicant, Third Order Sisters/Brothers, and the Affirmed (who also seem to be addressed as Sister or Brother, depending how you interpret Leliana's... everything).
Glossary (WIP)
lay people, laity: all members of a religion who are not part of the clergy (priesthood), including members of religious orders (monks, nuns, etc.)
ordination, ordained: the religious rite by which an individual is consecrated (literally, "made sacred") and, by virtue of that consecration, gains the authority to perform various religious functions ("sacraments"), primarily leading religious rites and ceremonies. Within Roman Catholicism (and some other Christian traditions) being ordained is to become a member of the "holy orders" (groups of consecrated individuals), of which there are three ranks: deacon, presbyter (priest), and bishop. Deacons have more limited authority than presbyters or bishops.
Within Catholicism there is a concept of "sacraments", which are holy rites that are believed to confer or "channel" the grace of their god to the recipient. There are seven sacraments; of these only baptism may be performed by a Christian lay person, and even that is usually done by an ordained person. Deacons can perform the sacraments of baptism and matrimony (marriage). Presbyters (priests) can perform the sacraments of baptism, matrimony, holy communion (the eucharist, the central rite of a Catholic mass (religious service)), reconciliation (confession), and anointing of the sick. Bishops can perform all of these sacraments plus the sacrament of Holy Orders--that is, ordaining people to make them deacons or priests or bishops. One bishop can ordain a priest or deacon, but it takes three bishops to ordain a priest into a bishop. Receiving at least some of the sacraments (Baptism, Reconciliation, and Holy Communion) is considered to be very important for salvation (reaching heaven in the afterlife) and one of the sacraments (Holy Communion) forms the core of the major daily or weekly religious ritual at the center of living a religious life.
Basic Organizational Structure
The Parish / Local Temple
The base of the Orlesian Andrastian Temple organization is the local temple or "Chantry". This is essentially equivalent to a real world parish. Every local Chantry temple is under the charge of a Revered Mother who is the pastor: the most senior priest (cleric) responsible for the care of the parish community. In small parishes, she may be the only ordained priest but in larger ones she may have a team of curates serving under her. The curates are ordained priests subordinate or junior to the Revered Mother, titled only Mother.
There are also usually deacons attached to the local temple, who assist the pastor with her Chantry's pastoral and spiritual mission. There is almost always at least one deacon attached to even the smallest Chantry and a Revered Mother has the power to install one should she find it necessary. Deacons must be affirmed or dedicated Sisters or Brothers, though it is rare and occasionally scandalous for Brothers to hold the role.
In addition to the pastoral team, there is the chancery staff, individuals responsible for the administrative tasks of running a Chantry. In the smallest Chantries, many or all of these tasks may be taken on by the pastor, curates, and deacons themselves. What and how many roles within a chancery are necessary varies widely based on a temple's region, role, and size. The positions within the chancery are most commonly filled by a mixture of lay people, ordained priests, and religious Sisters & Brothers. This is the most common place to find Brothers within the Orlesian Chantry.
In theory, every Chantry is entitled to a Knights-Templar detachment. This may be as small as a single Knight-Templar or, more usually, a 4- or 6-man lance, with the senior-most knight bearing at least the honorary rank of Knight-Lieutenant if he is not officially so. Rural, remote, and otherwise "less important" Chantries commonly face issues with getting or keeping Knights-Templar.
The Assembly (Diocese)
Parishes are grouped into Sacred Assemblies (name still a WIP), equivalent to a real world diocese. All of the local temples in a particular region are considered subordinate to the local Assembly, which is headed by a Grand Cleric. A Grand Cleric is approximately equivalent to a real world diocesan bishop. All Grand Clerics are members of the College of Clerics, the body which convenes to appoint by consensus a Divine who, by tradition but not writ, is one of their number. (Efforts to turn tradition into law on this subject are rare, and typically defeated by the argument that no strictures should be put in place which the first Divine, Justinia I, would not meet.)
Holy Provinces (Ecclesia)
All Grand Clerics are, in theory, equal... but some are more equal than others. Outside of the Orlesian heartlands, the Assemblies are grouped into Holy Provinces (real world ecclesiastical province or ecclesia), with one Assembly within the Province granted the status of metropole. The Grand Cleric Superior is the Grand Cleric of the metropole (aka the metropolitan seat) and has authority over any of the Grand Clerics within her Assembly. She may summon them for a clerical conference, a lesser version of the divine conclave to address regional matters. The Grand Cleric Superior is the one to whom the Orders of Accord and Third Orders ultimately answer to within a region, as these groups stand outside the standard parish system.
The Cathedral Curia & Grand Chancery
A cathedral is the temple where a Grand Cleric is stationed. Literally, it is the Chantry where her chair (cathedra) is located. She is the pastor of the cathedral parish, with a suite of subordinate priests filling the ranks of her curates and deacons. She is also responsible for, among other duties, assigning clergy throughout her Assembly, taking administrative and pastoral care of the priests and religious orders under her, and has the primary 'teaching authority' on matters of faith and interpretation of the Chant. The Cathedral Curia (literally, court) is the administrative body beneath the Grand Cleric concerned with her duties relating to governance of the Assembly. She must have, at least, a Vicar-General and a Chancellor. A Vicar-General is the Grand Cleric's "second-in-command", her principal deputy and the one who may act in the Grand Cleric's stead within the curia and the Assembly. She holds the title of Revered Mother and must be an ordained priest.
A Chancellor is the principal record-keeper of the Assembly and may have other duties relating to finances or personnel but is purely administrative in function and does not hold any spiritual authority. They may be an ordained priest, a member of a religious order, or a layperson (though this is very unusual), and bear only the title of 'Mother', 'Sister', or 'Brother' as appropriate to their religious vows. This is the branch in which it is most common to find Brothers. The Chancellor is in charge of the Grand Chancery, the administrative, bureaucratic wing of the Assembly's governance.
In addition to a Vicar-General (potential alternate name: aide-du-chanson?), a Grand Cleric may have multiple Vicars-Dedicant. Equivalent to real world episcopal vicars, they must be an ordained priest or Sister-Dedicate and function as aides for the Grand Cleric, similar in powers and role to the Vicar-General but with limited territory or focus (i.e. mission/topic in which they may act). A Grand Cleric Superior with charge of a Circle of Magi will (or should) appoint a Vicar-Dedicant focused specifically on Circle of Magi concerns.
The Grand Cathedral
From the date of its establishment, the head of the Orlesian Andrastian Temple has been the Holy Divine, based in Val Royeaux at the Grand Cathedral. The Divine is, technically speaking, the Grand Cleric Exaltant. Theoretically, she is the first among equals. She is chosen by consensus by a full gathering of the College of Clerics (the Grand Consensus) and is considered to be the heir of Divine Justinia I, the chosen of Andraste Herself. All Holy Provinces, all Assemblies, and all Third Orders and Orders of Accord are technically subordinate to her, including those--such as the Seekers of Truth--who stand outside the regular structure. Assemblies, and their Grand Clerics, which are not contained within a Holy Province answer directly to the Divine. Her seat is poetically known as the sunburst throne.
The Grand Curia is her bureaucratic 'court', equivalent to the Cathedral Curia of a Grand Cleric, but grander in scope and scale. She has multiple Vicar-Prefects with specific charges who act as her aides, filling different bureaucratic and diplomatic roles within the curia such as heading the assorted congregations (think: departments or ministries in a government), but no single Vicar-General. These Vicar-Prefects are all titulary Grand Clerics (i.e. Grand Cleric in title only, with no associated Assembly). Within this system is the High Chancery, the part of the curia specifically overseeing the finances and administration of the Grand Cathedral and the Divine's "household". The High Chancellor is in charge of this Chancery and is the highest rank to which a Brother may aspire. Also contained within the "household" of the curia are the Right and Left Hands of the Divine.
The Andrastian Orders
The Orders of Accord
The Orders of Accord is the formal name for the College of Enchanters, the Holy Order of the Knights-Templar, and the Seekers of Truth. The name derives from the Nevarran Accord which established these three groups and formalized the Circle of Magi system. These Orders stand outside the usual parish-assembly system. Pastors, curates, and deacons may be appointed to the physical Circles and their associated Templar garrisons, as well as to Templar garrisons which are not attached to a Circle. Each Circle is ultimately under the direct authority (and responsibility) of a Grand Cleric Superior (i.e. the chief Grand Cleric of a Holy Province or of a heartland Assembly that holds rank as a 'metropole'), who may appoint a vicar-dedicant specifically to take charge of Circle matters, although she may also choose to retain that office herself. The Seekers are a group apart yet again, being charged with oversight of the Circle, the Templars, and having judiciary roles regarding all matters of maleficarum and heresy. The Lord (or Lady) Seeker is technically subordinate to the Divine, but only by virtue of the Nevarran Accord itself where the Lord Inquisitor (later, Lord Seeker) Ameridan de Ghilain was a signatory equal to Divine Justinia I. How much authority the Divine can actually assert over the Seekers often depends very much on the individuals in question and the politics of the day.
The Knights-Templar maintain not only permanent garrisons in every Circle of Magi but also oversee a multitude of garrison-monasteries, dedicated to training or retirement, as well as regiments ex cathedra (literally, out of the cathedra, aka attached to a Grand Cleric's cathedral and responsible for the protection of all temples within that Assembly). All Knights-Commander are in charge of either a garrison or a regiment ex cathedra. Detached commands may be under a Knight-Captain (a rank also held by a Knight-Commander's SIC) or a Knight-Lieutenant and answer to either a garrison or regiment (command in absentia), a Seeker (command requisitia), or a Grand Cleric directly (command in divinia). There is a special detachment of the last kind associated with the Divine herself, taking orders from the Divine or her Right Hand: the Knights-Divine. The Templar ranks run approximately parallel to the Holy Orders, but an "equivalent" Holy Order rank generally outranks the Templar. (e.g. Grand Cleric outranks Knight-Commander, Revered Mother outranks Knight-Captain)
Holy Orders
Holy Orders refers to the primary priestly ranks of the temple: the ordained priests who have taken certain vows. These are the Mothers, Revered Mothers, and Grand Clerics, but also the Sisters- and Brothers-Dedicate. The Vow of Dedication are the only Holy Order vows that a man may take, as well as being the first set of vows required for taking the Holy Orders. Below these are the Affirmed, lay-people who have chosen to devote themselves to serving the Chantry and made certain affirmations, which are essentially temporary, voluntary vows. There are also initiates, who are typically children and essentially apprentices, receiving instruction and preparation for various roles within the Chantry, be that Holy Orders, the Knights-Templar, or the Third Orders.
Third Orders
The Third Orders are difficult to generalize, but are essentially all the various specialized monastic or spiritual ("religious") groups. Real world examples of this are the Jesuits, the Franciscans, Benedictines, etc. A member of a Third Order may also take Holy Orders and be a Sister-Dedicate, Brother-Dedicate, or Mother/Revered Mother. Monasteries, including the Templar garrison-monasteries, cloisters, abbeys, and so forth all fall under the Third Orders. A member of a Third Order will follow a specific Rule (such as the Rule of Saint Benedict) that governs how their community lives together. Many Affirmed who wish to dedicate themselves more fully to a wholly religious life go on to join a Third Order, entering as a novice and, eventually, taking sacred oaths (distinct from Holy Order vows). The most famous Third Order is, of course, the Chanters who may "speak only the Chant".