The Caste System

The society of The Empire is divided into rigid castes with extremely limited ability to move between them.

The Nobles

The nobles are the ruling caste.  From the emperor to mayors of small towns no one is eligible for public office unless they are born to a noble family.  Not all nobles hold an official position in the government, and nobles can be found at various wealth levels.  Not all nobles are richer than all citizens.  Nobles are easily recognizable by their names, all their last names end in -sis.  For example: Lansis, Tarksis, Silvaesis.  Nobles own the "gold economy", and it is technically illegal for anyone else to use gold as currency.  Gold coins are not in wide circulation.

The Citizens

Also known as free folk, the citizens make up the bulk of the population of the empire.  They have liberty to move from city to city, to change employment at will, and to get themselves into more trouble than they can handle.  The "silver economy" is said to belong to the citizens, but silver and copper coins are used frequently by citizens and nobles alike.  Citizens are allowed to own land, but not land to which peasants are bound.

Peasants 

The population of peasants has been slowly shrinking over the last several centuries. As the ice advances and the density of refugees grows, it becomes harder to return run away peasants to their home.  Peasants serve nobles, and nobles are required to pay for the peasants under their authority, but peasants are not bound to the nobles they serve.  Peasants are bound to the land, and if that land changes hands the peasants stay.  Peasants are restricted by the rules of the "copper economy", a particular set of rules where peasants sell their produce to their noble patron at a tenth of it's value and the noble must provide certain necessities to their peasants at a tenth of their value.

Indentured Servants

Slavery is illegal in the empire.  Indentured servitude is legally distinct from slavery.  Those who profit from the system of indenture are extremely keen to make sure that everyone knows that.  Any citizen who takes on a debt they cannot repay may be subject to a period of indenture to repay their dept.  Nobles cannot be compelled into indenture and other methods must be taken to settle debts.  Peasants are not allowed to accept credit, and anyone who thinks they are owed anything by a peasant has no legal recourse.

Child Indentured Servants

Although not legally distinct from regular indentured servants, the experience of children who are subject to this system is different enough that it's worth describing.  Starting when a child reaches adulthood at the age 20, they owe 10 years of unpaid service to whoever raised them.  Parents traditionally forgive their own children of this debt, but orphanages do not.  Because a child's contract of indenture is transferable, it's common for orphanages raise children up to the age of preteen or teen and then sell them off to serve as apprentices or laborers.