The Tenkou Courts are recent newcomers to the popular imagination of the citizens of the Dominion and the Faloran Republic. What is known about them is that they are a vast and seemingly undefeatable foreign horde which marched from the icy north of the world, where nothing should be able to survive, to the shores of the sea, establishing cities in mere days along the way.
Though some Tenkou have been captured by the Dominion for interrogation, there is not much which can be gleaned from them. What is known is that the Tenkou are a rigid caste society. They are led by Devourers and Homonculi; the Devourers being those who consume spirits for power, and eventually go insane. The difference between Devourers of the Tenkou and those outside seem to be that the Tenkou Devourers do not go insane - or if they do, it is a controlled insanity at worst.
In turn, many spirits are allowed to feast on humans, becoming Homonculi. It is theorized that part of the Tenkou path of ascension is ultimately an attempt to merge mankind with spirits.