The Lich King

The Lich King was once a mortal Sorceror-King who carved out a powerful realm around the Inner Sea, but was overthrown as his wars grew too taxing on his people. Unwilling to surrender his realm, he performed a dark ritual along with the most powerful lords still loyal to him and became the first Lich; an Undying skeletal creature with its soul forever bound to the mortal plane. Since then, he has held all undead creatures in his thrall to some degree or another. Through out history, desperate or strange mortals have found their ways into his ranks as well.

Wraith Lords
Seven Lords who followed the Lich King remain by his side today, they are known as the Wraith Lords and wield powerful magic and a modicum of control over all nearby undead creatures.

Clergy
Mortals who serve the Lich King recognize to some degree or another his power over undeath. Some willingly choose to revere him, and these mortals are granted boons in the domain of undeath. In exchange, the Lich King demands that undead be raised into his ranks and offered into his direct service.