  Type II theories can be described as the endpoint of closed string tachyon
condensation in certain orbifolds of supercritical type 0 theories. In this
paper, we study solitons of this closed string tachyon and analyze the nature
of the resulting defects in critical type II theories. The solitons are
classified by the real K-theory groups KO of bundles associated to pairs of
supercritical dimensions. For real codimension 4 and 8, corresponding to
$KO({\bf S}^4)={\bf Z}$ and $KO({\bf S}^8)={\bf Z}$, the defects correspond to
a gravitational instanton and a fundamental string, respectively. We apply
these ideas to reinterpret the worldsheet GLSM, regarded as a supercritical
theory on the ambient toric space with closed tachyon condensation onto the CY
hypersurface, and use it to describe charged solitons under discrete
isometries. We also suggest the possible applications of supercritical strings
to the physical interpretation of the matrix factorization description of
F-theory on singular spaces.
