Echoir
Echoir is a plane which is visited by Dack Fayden in The Spell Thief comic #1. The only area seen is a giant titan's castle. The Titan Collector collects creatures from other planes in magical "arrest" spheres. A notable creature that attacks Fayden is a Cateran, from Mercadia.
Sifa Grent is in contact with the Titan, and has visited before.