So you want to play a divine magic caster, aka a theurgist?

Who is your source of power?

It is "who" and not "what". All divine magic in Scarterra comes from the Nine. Most divine casters have one of the Nine as their sole source of power while a rare few derive their magic from the Nine collectively.
You must choose one of the Nine as your character’s patron or play a pantheon caster.

Many fantasy RPG settings treat divine magic as just a simple mechanic or an afterthought, but the lore of Scarterra is built on the foundation of the lore of the Nine. Divine Lore is the first category in the table of contents for a reason. If you as a player don't want to get entangled in that aspect of the lore, you probably shouldn't play a divine caster.
You don't have to read everything, but you should at least read the full article on your character's patron god or goddess and their related follower articles.
The quickest way to browse the basics of the Nine without reading everything is the brief stats articles.
Maylar stats in brief
Mera Stats in brief
Korus Stats in Brief
Nami stats in brief
Greymoria stats in brief
Khemra stats in brief
Zarthus stats in brief
Hallisan Stats in Brief
Phidas stats in brief

How did your divine power manifest?

Favored souls are born with their divine magic foisted upon them while annointed gain their magic as a result of their piety and focused will. Most annointed are trained in a religious order from a young age, but a large minority of them are self-taught theurgists from a secular background.

Favored souls are sometimes treated differently from annointed by their own respective priesthoods and general society, sometimes they are not. Most favored souls have periodic visits from a spirit that acts as a mentor of sort. At the very least, a spirit shows up at least once to explain to a young favored soul who and what they are.

by Me with Hero Forge

You want to consider your character’s upbringing and education before you start filling dots on your character sheet. A theurgist trained in a school-like monastic setting is going to have a different set of skills than one who followed a mentor and learned on the job out in the field. Both are going to be different from a self-taught annointed or favored soul who grew up initially aspiring to be something other than a holy figure before it was thrust upon them.

Social Connections and background

Players should give thought to their character background and social connections with any character and consider using Merits and Flaws to flesh this out.
For a divine spell caster, social Merits could involve favorable relations with your divine patron’s priesthood while social Flaws could involve unfavorable relations, or perhaps you attracted the attention of your divine patron’s rivals.

You should figure out if your character is an ordained priest or priestess or if he or she is associated with a holy order of some sort. This is not required, many divine casters have no formal ties to a priesthood, knightly order, or monastic order. It is also possible to play as a priest, holy warrior, or monk to be a part of a holy order and not have any divine magic at all.

That doesn’t mean your character has to be defined solely by their divine connections. Annointed and favored souls are still people and often have families, friends, rivals, hobbies, and professions not enmeshed in temple politics, though some theurgists have very little to their lives outside of their holy calling, especially if they began their religious training as children.

Is your character a loner or he part of an existing holy order? If so, is he part of a large and mainstream holy order or a small fringe group? Does he get along well with his temple hierarchy or does he butt heads with his ecclesiastical superiors?
All Scarterrans worship the same nine deities (or at least acknowledge the same nine deities but they don't agree on the right way to do it. It is worth keeping in mind during character creation and coming up with your background how well your character's religious organization fits into society at large, or at least the society your character was raised in. Some religious organizations are powerful and respected or at least one of these two things while other religious organizations are obscure and largely unknown or even outright shunned and feared. Certain religious organizations are often associated with the upper classes and others are associated with the lowly riffraff. This will impact your character connections and abilities.

Power Optimization of your points buys

You only have so many freebie points and experience points. Some divine casters put the lion’s share of their points into their magical abilities and others only put a few points into their magic.

Technically, you only need a single dot of divine magic to be a theurgist. One dot of divine magic is enough to use divine wands and scrolls. If a holy order or priesthood requires theurgy to hold certain ranks, one dot is usually all it takes.

Tihalt by Eron12 using Hero Forge

by Eron12 with Hero Forge

It is easy for holy warriors to resemble D&D paladins or rangers. They only have a little bit of divine magical ability and rely primarily on their fighting skills. Holy warriors in Scarterra are fairly common and are present in every religious group to some extent. You can also play a diplomat, a sneak thief, or craftsmen that happens to have a bit of divine magic.

If you decide to really lean into your divine magic, your not going to have as many nonmagical abilities to fall back on. This is no problem if you like playing a support character to help your allies shine. It is certainly a viable strategy to load up on as many dots of divine magic as you can afford and hide behind your adventuring party’s strongest warriors while casting spells to make them stronger.

If you want to play a more frontline action oriented character, it’s better to go lighter on a divine magic. It’s a viable play style to cast a couple spells early in the combat (or in the immediate preface to combat) to tilt things in your favor, then start swinging weapons.
Both play styles are viable, but you should build your character towards which ever style you think would be more fun to play.

You definitely don't have to play a stereotypical D&D or Pathfinder Cleric who does nothing outside of healing and buff spells while his/her allies do all the offensive stuff, but if that kind of character interests, it is easy to make that style of theurgist, especially with a Mera affiliated theurgists since Mera's favored spheres are Healing, Protection, and Purification.

There are 13 spheres of divine magic, you cannot realistically have them all or at least you cannot have them all at a five dot rating. Do you pick the favored spheres of your divine patron or do you pick what seems most useful and fun? If you need help deciding what divine spheres work best for you, the article Divine spheres, quick reference guide should help you out a lot with quick links to easily find the full descriptions if needed.

Every divine sphere has an attribute and ability combination to cast them. You should consider picking divine spheres that match attribute + ability combinations that you have high ratings, or you should consider assigning high ratings to attribute + ability scores connected to divine magic that you find most appealing. Again the Divine spheres, quick reference guide should help you plan out your character accordingly.

20 d10s from Wikimedia Commons

A lot of divine magic uses Theology or Enigmas, 6 of the 13 spheres in fact. In terms of spell effects, it makes zero difference to the potency of the spell whether a character casts magic with Theology or Enigmas, but it makes a difference to the character's personality and background. Characters that rely on theology are likely to be ritual and tradition focused, focused on what is known as orthopraxy, doing the religious observances exactly right.
Characters that rely on Enigmas are more inwardly focused and focus on meditation and reflection, and building a personal relationship with their divine patron, in other words, orthodoxy.
To put it simply, do you picture your character burying his nose in holy texts or quietly meditating in the wilderness to become one with the universe?
You can of course play a character that has a high rating in Enigmas and Theology. Such a character would be a very spiritually balanced teacher and sage which can be fun to roleplay, but from a metagame perspective if you goal is to maximize your spell casting prowess, it is better to load up on dots in one of these traits, not both.
Each deity has three favored spheres which give their affiliated casters a difficulty break when using them. Pantheon casters can choose three spheres form a short list. This is handy, but you are not required to take all three of your favored spheres. In fact, you are not required to take any of your deity's favored spheres at all.

It is also possible to purchase a special merit to give your character a fourth favored sphere based on your character's personal aptitude rather than your character's deity's aptitude. Early playtesting shows this is a very popular option with players. If you are basing your character’s contribution to your party on one sphere, you should consider taking the “Additional favored sphere” Merit. It costs four freebie points, but it’s potent if you pair it with a utilitarian sphere that is useful for you and your adventuring party.

by Eron 12 with Hero Forge

In early playtesting, casters that focus on a small number of divine spheres at a high level tend to outperform casters that that focus on a wide array of divine spheres at a low level, at least in combat.

Most of the one dot divine powers are sensory based. Most of the utilitarian magic that adventurers need routinely are clustered around the three dot level. Four and especially five dots divine magic powers are not normally magic for everyday situations. They are miracles to be called on in times of great need. Most Scarterran theurgy wielders rarely reach these lofty heights and those that do are expected by their priesthoods and societies to use this great power judiciously. Characters with four and especially five dot magic powers are likely to be regionally famous and widely sought after for good or ill.

Willpower is useful to all characters, but when playing a divine caster, it also impacts your mana pool making it even more valuable. You should raise your Willpower score as high as you can justify or afford. In fact, annointed are required to have at least five dots of Willpower.

Brigid in Heroforge by Eron12 on Heroforge

Divine Bard gives you enough freebie points to cover being a divine caster and your first dot of magic, but it limits your ability to cast magic discretely forever. Put some careful thought into all the Merits and Flaws for divine spell casters, not just Bardic Caster.

If you choose high level Spirit Magic, you should have a relatively high Wits score. Spirit magic is cast with Charisma but it is maintained with Wits. The maximum amount of summoned spirits or conjured elementals you can have in play any one time is limited by your Wits.

Ragani portrait by Eron12 using Hero Forge

by Neshik's Player with Hero Forge

If you choose to take divine Crafts, you likely to want to create potions, scrolls, arrows and other finite magical items someday and you should thus familiarize yourself with the rules article: Player Characters creating finite magical items. The rules are a little wordy, but if you have high ratings in related skills, you can make magical items quicker and cheaper and this is very useful.

For instance, having a high rating in alchemy helps you make potions and at a decreased difficulty. Having a high rating in archery lets you make magic arrows at a decreased difficulty. It’s worth keeping this in mind when assigning your initial traits. Some players find this sort of math tedious and others find it fun and engaging. If you are in the former category, you probably shouldn’t take divine Crafts and just buy your potions and other magic items.

If you take Wrath, you should have the fighting skills to back this up, especially archery once you get to three dots and above because all these powers use archery to aim the attacks.

If you want to dive really deep into the weeds

How mortal divine magic fits into Scarterra covers every divine sphere in detail of how their magics are commonly used and how they impact Scarterra society at large.
This is admittedly long. It is unnecessary to read any of it to make or play a theurgist character, but it handy for players who want to make a deep dive into background and the related setting lore.