Zeiram the Lich

Zeiram was a tortle who pursued life after death by becoming a Lichdom. Trapped underground in 772 by a gnome and Mul expedition in a Cerulean lair she had created for herself half a century prior, she survived by dint of her phylactery being well hidden above ground where it lay, undiscovered, for nearly two hundred years.
The phylactery was discovered by a human Wizard exploring Cerulea's ruins. The Wizard, named Rosta, found the phylactery and traced Zeiram to the dungeon in which he had been imprisoned for two centuries, releasing the Lichdom from what she had come to view as a mistake during her long incarceration.