anointed

Technically, theurgist is the broad term for all divine casters and includes anointed and favored souls, but because anointed are so much more common than favored souls, some Scarterrans use the terms "theurgist" and "anointed" interchangeably.
Divine spell-casters are all either anointed or favored souls. favored souls are born with divine magic powers and anointed gain their magic later in life.
Mortals need three things to become an anointed. They need strong wills, great focused piety, and a strong focus on a skill or a set of related skills. Of these three requirements, focused piety is the requirement that eliminates most Scarterrans.
Most anointed are mortals who pray exclusively or almost exclusively to one deity. A rare few are mortals who pray to the Nine collectively and worship all nine of the Nine equally.
Most Scarterrans are polytheists praying to all of most of the Nine, but most play favorites. These two things prevent most Scarterrans from developing theurgy.
If a mortal has the willpower and the piety to become one of the anointed, their first powers will manifest as extensions of their ordinary skills and aptitudes. A practitioner of medicine is likely to develop Healing magic. A warrior is likely to develop offensive or defensive magic. An herbalist is likely to develop Plant magic.
Not every theurgist is a priest and not every priest is a theurgist, but most anointed theurgists were recruited and trained by a priesthood, either one of the Nine's priesthoods or the Cult of the Compact. About one-in-four anointed are self taught developing the willpower, piety, and skill focus to channel divine magic without formal training.
In most cases, the various priesthoods are happy to welcome self-taught anointed into their ranks (they wield the power of their deity after all), but occasionally there is friction between self-taught and more formally trained theurgists. A lot of schisms within priesthoods are the result of a charismatic self-taught anointed breaking away from the priestly traditions and teaching apprentices his or her take on how worship should be performed which may or may not catch on wide enough to be passed to future generations.