Lys is the dimension in which most of the Lys Trilogy takes place. Its pronunciation /līs/ or /lis/ is up for debate, yet irrelevant. In the writer's mind it always sounded like /lis/.
Lys was created in the dimension of Biz as a means to provide copious amounts of energy, enough to solve the crisis of not having enough to build the factories and malls that they felt were necessary. It was found impossible to create only one dimension, and so a Twin-Dimensional Engine was created, which almost ended in total catastrophe.
Lys is only half of the engine, Syl being its twin. Syl is unstable, chaotic, held together by the Spirit Symbol of Lys.