Morisant was the Chief Architect of Zzyzx. A "True Wizard". Due to the character flaw of Hubris, Morisant attempted to cheat death (as even Wizards age, although incredibly slow). He Turned himself into one of the undead to cheat death. Turning into an undead caused Morisant to lose most of his senses and gained new undead hunger. Due to this, Agad, and other Wizards, bound and imprisoned Morisant, which turned him mostly to stone. He refused to give up his sword Vasilis, and the other Wizards lacked power to take it, so Morisant was hidden away and became the guardian of the sword he wielded in life.
For Seth to take the Sword, Morisant requires Seth has to end Morisant's, and the Standing Undead's, suffering.