The city of Erast is entirely built on and out of, one unnaturally large slab of marble. The various shades of marble were used to denote the districts of the city; Black, Blue, Red and White.
As a port city it often deals with The Union trading goods luxuries and even slaves. As with other cities in Praellara it benefits from the use of slave labour to manufacture goods, work lands and build infrastructure. Visitors to the city do not need to stay long to recognise there is a slave class and they are not well treated.