Vikingeborgen Trelleborg

The unfree
Slavery and serfdom seem objectionable today. The thought of one man
owning another offends our concept of morality. But in the world of
the Vikings, slavery was probably not “evil” - it was a condition of
life. A human being had value only as a part of a group or family.
Purchase and sale
Thralls were unfree. They were owned by another man, and therefore
had no right to their own life. They were either bought, or obtained
in raids around Europe. The main goal of many Viking raids was the
acquisition of thralls for their own use, or for selling.
Contemporary sources tell of slave markets in Denmark. Ansgar wrote
in the mid 9th century how thralls were traded in Haithabu (Hedeby).
Large farmsteads were partly self-sufficient in thralls, as the
child of two thralls automatically became a thrall. We do not know
the number of thralls in Viking Age Denmark, but they must have been
present in most farmsteads which could afford them. The work of
thralls could vary greatly, but it must primarily have involved hard
physical labour.
The thralls given freedom
It was possible for a thrall to be given their freedom, or to buy it
themselves. The Icelandic sagas describe in several places how a
master would free a thrall if he or she had deserved it in some way.