  In this paper we construct a one-dimensional insulator with an approximate
chiral symmetry belonging to the AIII class and discuss its properties. The
construction principle is the intentional pollution of the edge of a
two-dimensional quantum spin Hall insulator with magnetic impurities. The
resulting bound states hybridize and disperse along the edge. We discuss under
which circumstances this chain possesses zero-dimensional boundary modes on the
level of an effective low-energy theory. The main appeal of our construction is
the independence on details of the impurity lattice: the zero modes are stable
against disorder and random lattice configurations. We also show that in the
presence of Rashba coupling, which changes the symmetry class to A, one can
still expect localized half-integer boundary excess charges protected by mirror
symmetry although there is no nontrivial topological index. All of the results
are confirmed numerically in a microscopic model.
