The Four Horsemen

The Four Horsemen, also refered to as the archdaemons, are powerful daemons having attained the strength of demigods. They rule Apollyon, and have hordes of daemons in their service. Each of the Four Horsemen represents one of four ideals: war, pestilence, famine and death. Unlike archdevils and demon lords, the Four Horsemen have been present in Apollyon since the genesis of the realms, and are seemingly immortal, and cannot be replaced or usurped.

From left to right.
Charon, Horsemen of Death atop his steed Chloros
Balishek, Horsemen of Famine atop his steed Halflight
Sisera, Horsemen of War atop his steed Grace of the Flame
Roshmolem, Horsemen of Pestilence atop his steed Septisaeus