About the peoples: tweni

The tweni are a recent addition to the series. Suffice to say, a tweni is a half-valkyrie. Mhaldin and Fenera are tweni (see their entries under About the Characters). Though they originally reproduced by meditating underneath the roof of one of eight towers, valkyries began to die off when the towers they needed were destroyed by Usor'an. Thus, they died out. The tweni arose from unions between humans and valkyries.
A tweni is physically identical to a human, though the females tend to be better built than human females (owing to their valkyrie heritage). The most unique trait about tweni is, like valkyries, they are born in pairs. Unlike valkyries, only one twin is a girl. The bond between tweni twins is the strongest attachment in the worlds. Not only do they have an unshakable devotion to their twin, tweni also can share minds with their sibling (see Fenera or Mhaldin's entry for more details). This bond is so strong that a tweni has never killed their own twin. This fierce commitment also means that incest rates are extremely high amongst tweni.
The tweni do not have a society. They are a scattered, leaderless people living as dregs in the underworlds of Eray and Jindaria. They do not have any political alignment, instead believing themselves to be a secret nation that will one day claim its rightful place in the world.
Since tweni have a high birth-rate, they are often enslaved en mass and bred like cattle for the females to serve as workers while the males are made soldiers to fight the demons: the main antagonists of my series. Because of this forced-breeding, the tweni have a substantial population despite their relatively recent addition to the world.
Males are valuable soldier material because they can constantly commune with their sisters, earning them an instant return to their home, even in the heat of battle. Tweni soldiers are famous on Eray and Jindaria for having high morale. What's more, they train and experience war. If their sisters choose to follow them into the army, they will already be more experienced than most recruits.
Tweni have no distinct culture. However, their rising numbers will soon make them a force that is formidable enough to break from enslavement and integrate into the worlds are a true influence.