Ankou is a spirit who serves as the demigod of death. He is not responsible for death occuring, but rather oversees it, shepherding lost souls to the appropriate afterlife and empowering cleric to hunt down and destroy the undead, as well as those who extend their lifespans, such as through the blessing of the Oluana Spring.
These priests, known as The Shepherds, worship Ankou at a series of lighthouses which house separate beacons for both the living and the dead.
Much as Raos drives a chariot across the sky accompanying the sun, Ankou drives a cart across the Shadowfel, carrying the lost to safety. His lantern is visible to the living as normal light, but also acts as a great beacon to the dead, as his lighthouses do.
Ankou was not originally part of Demonac's worldbuilding, but was added to accomodate the character concept proposed by Zaheer's player, along with The Shepherds. Rygax predated this, but had little detail, simply being a famous Vampire hunter who lived in the Shadowfel.
The correct spelling of the demigod's name is questionable, with Ankou, Ankhou and even Enku turning up in Demonac's notes. The editorial decision to be wildly inconsistent across the wiki is a reflection of this and not of the editors' indolence.