  In this paper, we establish the quaternionic versions of the potential
description of various "small" sets related to the quaternionic
plurisubharmonic functions in $\mathbb{H}^n$. We use the quaternionic capacity
introduced in \cite{wan4} to characterize the $(-\infty)$-sets of
plurisubharmonic functions, as the sets of the vanishing capacity. The latter
requirement is also equivalent to the negligibility of the set. We also prove
the Josefson's theorem on the equivalence of the locally and globally
quaternionic polar sets in $\mathbb{H}^n$, following the method of
Bedford-Taylor.
