The joga are a race of constructs, although they would never describe themselves as such. They look like stylized humanoids made from brass and wood. They take pains never to look to similar to humans, as they would never like to be confused with a human, and they would never like a human to treat them as more than a tool.
They live inside churches, and rarely leave their designated chambers. They are memory-keepers, able to record their memories perfectly, copy them quickly, and trade them among themselves. These memories are stored as copper rods, which are kept into their chest. (Their heads are usually full of their bulky optical and vocal apparatuses.)
The downside to their impeccable memory is the size of it. Each joga's capacity for memory is much smaller than a human's, and surplus memories must be stored outside of their body. Each joga must decide what knowledge/memories/goals are important enough to keep loaded (in their body) and which must be kept on the bookshelf.
Because daily activities are seldom of any great importance, it is common for a joga to fail to recognize you from day to day. They are like a microscope--seeing a tiny part of their own history, but with an immense level of detail.
Joga: "Good morning, brother. Have you come to worship the prophetess (may she live again)?"
Korgoth: "I was here on April 9th, asking about a demonic weasel. You said you would research it for me."
Joga: "Seek patience." [finds and inserts the relevant memories] "Ah yes, the musteloth. It was described by St. Gwinnious of Fynn. . ."
Each Joga usually keeps an index of their important memories, usually a tome of some sort.
They "replay" their memories by speaking. Each of them is an impressive caricaturist and vocal impersonator. It is believed that they can never lie.
They illustrate their memories by painting. Each of them is a technically masterful painter, and each of their fingers is capable of wielding a paintbrush independently.
Each generation of Joga is built by the previous one. The secrets of this manufacture are not shared with humans--it is the only secret that the Joga keep.
This is their rationale for such secrecy:
The joga are perfect, and exist only to serve the Church. Humans are not perfect. If humans were allowed to create a joga, they might create an imperfect joga, and thus corruption may spread down our line.
It is a mistake to think that they are creatures composed entirely of logic, without any emotion. They are stoic, yes, but they also mourn, laugh, and grow wrathful.
Above all, however, they insist that they are not alive. In their own words, they are just "mechanisms undergoing a very complicated unwinding". They will destroy themselves if ordered to by a high-ranking member of the Church. (They will cry during this, although they will deny that they feel any sadness.)
Usually, however, the Church will order the joga to simply melt down their brass rods, effectively rebooting the joga.
Because their memories are so easy to isolate and erase, the Chuch usually employs them to identify and catalog heresies.
Because heresies constitute a moral hazard (they imperil your soul's ability in the afterlife), it is not uncommon to spread knowledge of a heresy across multiple joga.
Alternatively, heresies are sometimes summarized through several joga (or more reasonably, the same joga in different states), by wrapping the heresy in layers of summary and encoding (such as translating parts to a different language that the joga currently has no understanding of).
For example, each paragraph of a heresy can be encoded in a different language. By cycling languages, a joga can access each paragraph quickly and individually, without being exposed to the corrupting effect of the whole.
Joga were purchased from the Tamberlanders, who are their ancestors.
Most people know them as the balloonists: mad, goggle-eyed men who fly across Centerra in harnesses suspending from balloons.
The balloons are (mostly) alchemical, and can fold up and fit into their own backpack, which is attached to the harness that each tamberlander wears. The balloons quickly break when not in the possession of the tamberlander. They are tricky devices to maintain, and the tamberlanders maintain their secrets well.
This allows them to drop in and out very quickly.
Their faces are fake, and their fingers are cold. They will remove both when they believe themselves to be alone. They communicate to each other by sticking their rod-like "tongue" into the ground--which is inconvenient for a race that spends so much time airborne. (Or at least, the tambermen you meet in Centerra will most likely be travelling balloonists).
Sleeping is performed in a similar way. Face in the dirt, anchored by their tongue, feet in the air, body stiff as a rod.
Like the joga, they are primarily made from wood and copper, along with clever prosthetics they use to hide their nature. They are also a race of constructs, but believe themselves to be people just like any other. Most are mildly contemptuous of the Church. Most of the ones you'll meet in Centerra are a bit mad, and tend to have strange obsessions.
They're renowned as scouts and traders. Most will hire themselves out for a high price, or trade in small, transportable valuables: saffron, sapphires.
In their homeland, power is correlated with having the most descendants, who are (mostly) loyal to their creators. But since it takes a tamberlander over a year of labor to build a child, and the parts required are costly, it is not easy to quickly raise an army.
Parts can be quickly obtained by killing another tamberlanders and scavenging their parts, but this is as risky as murder is in our society. Although this does seem to be the prior norm. Only the current power structure in Tambool seems to restrain them, allowing (because of) aggression against Yog.
Their homeland is far to the north, across the deserts of the Madlands, past the Infinite City of Yog. They live on the Isle of Tambool, which is not an island but a mountain.
Tambool is described as an island because it rises above a sea of poisonous fog. The tamberlanders produce the fog themselves through their alchemy, as a defense against invasion. Being constructs, the poison doesn't harm them directly.
The tamberlanders have declared war on the Infinite City of Yog, which has not yet noticed. (The messenger is, presumably, still threading his way to the throne room of that great city). But they will, eventually, and when that happens, it is best to hide behind a giant poisonous cloud.
Until then, their bombing campaign continues, which is similarly unnoticed in Yog.
A city has a great deal of needs, besides food and farmland, and for this reason the tamberlanders are constantly venturing out on their balloons and ekubas (undead horses, usually purchased from Kel Dravonis).
It is not known how the Church came to purchase the children of the tamberlanders, what they paid for it, or how their progeny was ultimately transformed into the (very different) joga.