A necropolis in the Dreamlands referenced in The Codex of Three Prescriptions, Manual of Silence, and The Unified Manual of Understanding, three of the books in Lowls' footlocker.
In Chapter 101, the party learned that the city had a long and apparently tragic history, and that the Leng Ghouls that dwelt there were known for bejeweling and enchanting the skulls of their greatest kings and queens, including Queen Chalthas.
In Chapter 130, the party arrived in Igguzqaiz on their quest for the Skull of Ghoul Royalty. It was a massive underground necropolis metropolis, caught in the middle of a war between an army of cats and an army of Gugs. From Buszha, the party learned that after Rony/The Triangle Man stole the skull of Queen Chalthas in the past, the Leng Ghouls were filled with despair and abandoned the city. The cats found it and moved in, but were quickly assaulted by hordes of Gugs looking to claim it from them.
First Reference: Chapter 90
Other Notable References: Chapter 101, Chapter 130, Chapter 131, Chapter 132, Chapter 175