Harz-Takta the Senseless was a black robe wizard considered too nefarious to stay in the black robes. Little is known about the Renegade Wizard who was active around the year 750 PC. They are primarily known for a single surviving spellbook.
The spellbook reviews the known history of the Lost Citadel. It speculates that there are a dozen magical sites across Krynn that can be used for interdimensional travel. The book contains an unconventional spell that can be used on the Night of the Eye at one of those gates (a different one each time) which will open a portal to the Lost Citadel. The book ends with Harz-Takta's notes before attempting the spell. A little before 339 AC, the spellbook was recovered from the Coral Oracle in Itzan Klertal by Belize who summoned a demon to fetch it.