\documentclass{article}

\usepackage{mkessler-mathop}


\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}   % loads »amsmath«
\usepackage{graphicx}
\usepackage{relsize}

\DeclareMathOperator*{\name}{\raisebox{-0.5ex}{\scalebox{2}{$\ast$}}}


\begin{document}

 a = b = $\name_a^b cd\sum_a^b \int_a^b \name_a^b$

\[
A\name_C D\name_a^b \sum_a^b
\] 

\[
    \Gal \Quot \PreSh \tensor \Var \Br \Set \CHaus \cfun \One \left\lfloor \frac{1}{\frac{3}{\frac{7}{8}}} \right\rfloor \abs{\frac{1}{\frac{8}{\frac{4}{3}}}}  \lVert \frac{a}{\frac{b}{c}} \rVert  \left< \frac{a}{\frac{b}{c}} \right> \norm{\frac{a}{\frac{b}{c}}} \norm{test}  \norm{\frac{a}{\frac{b}{c}}}
\] 
\end{document}
