  We study the $\kappa$-Borel-reducibility of isomorphism relations of complete
first order theories by using coloured trees. Under some cardinality
assumptions, we show the following: For all theories T and T', if T is
classifiable and T' is unsuperstable, then the isomorphism of models of T' is
strictly above the isomorphism of models of T with respect to
$\kappa$-Borel-reducibility.
