We present the first fully nonlinear study on the accretion of scalar fields
onto a seed black hole in anti-de Sitter spacetime in Einstein-Maxwell-scalar
theory. Intrinsic critical phenomena in the dynamical transition between the
bald and scalarized black holes are disclosed. In scalarizations, the
transition is discontinuous and a metastable black hole acts as an attractor at
the threshold. We construct a new physical mechanism to dynamically descalarize
an isolated scalarized black hole. The first results on critical phenomena in
descalarizations are revealed. The dynamical descalarizations can be either
discontinuous or continuous at the threshold, distinguished by whether or not
an attractor appears