Okay! Here's what I've come up with:
A pine kindred jarl is a mighty undead chieftain who rules a tribe of pine kindred. These spellcasters look like pine kindred thanes but often have elaborate crowns, horned headdresses, carved staffs and other complex paraphernalia that reflect their status, especially when the jarl performs spells or ceremonies.
Pine Kindred Creation. The jarl is usually the only pine kindred in a tribe able to create full-blooded pine kindred using the Pine Kindred Initiation power. Due to this, the tribe’s pine kindred view the jarl not just as their ruler and prophet, but as their parent; considering themselves all to be daughters or sons of the jarl (Note this disregards the gender of the humanoid the tribe member was when alive: thus, If the jarl is viewed as female, all the tribe members are “daughters”). Powerful jarls are also able to produce full-blooded pine kindred using a Dark Druidic Mystery spell called create pine kindred, similar to the necromancy spell create undead.
Groves of Death. A jarl performs most of their important magics, especially the Pine Kindred Initiation ritual, in an unholy grove. These are gruesome places where ancient living and dead pine trees loom over blood-soaked altars, ancient stones and wooden idols, all carved with occult runes. The jarl and their attending thanes dwell nearby in the Jarl’s Hall.
Jarldoms. The territory of a jarl is called a jarldom. A pine forest may contain a single jarldom, but large and ancient forests may have multiple jarls within them. If two or more pine jarldoms exist in close proximity, they will either be deadly rivals or one of the jarls will rule over the others. Such a pine king may be no more powerful personally than its subordinate jarls, although it often is, and is almost always the ruler of the oldest and largest pine kindred tribe. The jarls under the king’s command are usually former thanes of his that progressed far enough in the Dark Druidic Mysteries they became jarls in their own right. Once a pine kindred becomes a jarl they found their own tribe of pine kindred apart from their parent community. Relations between jarldoms can be as complex as mortal politics, with much jockeying for power and prestige, which often includes espionage to try stealing the magical secrets of a rival jarl. It’s rare for a subordinate jarl to not be a descendant of the king’s sapline, such jarldoms are effectively conquered territories and far more likely to rebel.
I think that'll do.