  In general there are a large number of light scalar fields in the theories
going beyond standard model, such as string theory, and some of them can be
taken as the candidates of curvatons. For simplicity, we assume all of
curvatons have the same decay rate and suddenly decay into radiation at the
same time. In order to distinguish this scenario from the more general case, we
call it "N-vaton". We use $\delta {\cal N}$ formalism to calculate the
primordial power spectrum and bispectrum in N-vaton model and investigate
various bounds on the non-Gaussianity parameter $f_{NL}$. A red tilted
primordial power spectrum and a large value of $f_{NL}$ can be naturally
obtained if the curvature perturbation generated by inflaton also makes a
significant contribution to the primordial power spectrum. As a realistic
N-vaton model, we suppose that the axions in the KKLT compactifications of Type
IIB string theory are taken as curvatons and a rich phenomenology is obtained.
