\newcommand{\spellheader}[6]{
  \subtitlesection{#1}{#2}
  \vspace{-1ex} % subtitlesection artefact; topsep also changes bottom spacing.
  \begin{description}[font=\normalfont\textbf,noitemsep,topsep=1ex,leftmargin=1em]
    \item[Casting Time:] #3
    \item[Range:] #4
    \item[Components:] #5
    \item[Duration:] #6
  \end{description}
}

\newenvironment{spell}[6]
  {\spellheader{#1}{#2}{#3}{#4}{#5}{#6}}
  % Environment encloses description.
{\vspace{\baselineskip}}