Shattered Empire Introduction (2001)

From Introduction:

300 years ago, the Celestial Emperor, the last ruler in a line demi-gods was killed by an assassin who was in league with unspeakable horrors from another dimension. Fortunately he was killed by one of his followers just before he was able to complete the rituals to suck the real world into the shadow realm. The mighty Empire, however, shattered into various factions ruled by warlords.

Today, most of the land is overgrown by jungle. The wilds are home to many weird creatures (often mutated by the influence of the shadow plane). Only a few humans survived and have built new
cities. These cities are ruled by the descendants of the warlords, most of which have acquired mystical powers over the generations These rulers are accepted because they provide stability in a dangerous wilderness. The North is largely unified under the iron rule of foreign horse nomads who have kept the local bureaucracy largely intact.