Niko
Niko is a demon horde leader, master of a horde that nearly rivals Char's horde in power. The two demon gangs are constantly locked in battle with the other.
This is the horde that attacks the hunter squad out on the field, when Christina, who had been accompanying Astasia and Zerek's team on a hunt, accidentally allows a demon they recently captured, to summon Nikko for aid. The horde overwhelms the group of hunters as they flee to the safety of their kingdom, but ultimately brings upon the death of Zerek, and thus Astasia's determination to bring him back, begins.
Later on, after the Hunter Kingdom is destroyed, Niko falls in battle against Char, whose horde is now twice, or three times as powerful as it was before the kingdom's fall. With Niko eliminated, Niko's already large horde, merges with Char's, giving Char even more unrivaled strength and the power to flatten any kingdom and anything that apposes him, to the ground.