Liches are former wizards or enchanters that prolonged their lives by becoming undead. Some reside in the Grim Marsh at Fablehaven. More intelligent than a Zombie, a lich appears desiccated or completely skeletal. They have the ability to control lesser Undead creatures and use them as servant soldiers. As they are undead themselves, they are connected to the Underking and the Under Realm.
In Keys to the Demon Prison, Patton suggests conscripting liches from the Grim Marsh as an alternative to recruiting wraiths to guard the fallen preserve. Although unconfirmed, by definition, Morisant nearly became a lich.
In Master of the Phantom Isle, Seth bargains with the powerful lich Belrab, who then leads the prisoners out of the Blackwell to overthrow Wyrmroost. Another lich, Ezabar, watches over the imprisoned Bracken on behalf of Ronodin. Stavius guards the Underking and is obliterated by Kendra when she retrieves Bracken and the Sunset Pearl.