  We describe a deformation of the $\infty$-category of Borel $G$-spectra for a
finite group $G$. This provides a new presentation of the $a$-complete real
Artin--Tate motivic stable homotopy category when $G=C_2$ and gives a new
interpretation of the $a$-completed $C_2$-effective slice spectral sequence. As
a new computational tool, we present a modified Adams--Novikov spectral
sequence which computes the $RO(G)$-graded Mackey functor valued homotopy of
Borel $G$-spectra.
