We discuss the universal theory of localized impurities in the paramagnetic
state of 2D antiferromagnets where the spin gap is assumed to be significa
ntly smaller than a typical exchange energy. The study the impurity spin su
sceptibility ner the host quantum transition from a gapped paramagnet to a
Neel state, and we compute the impurity-induced damping of the spin-1 mode
of the gapped antiferromagnet. Under suitable conditions our results apply
also to d-wave superconductors.