  For decades, physicists have analyzed various versions of a ``cosmic no-hair"
conjecture, to understand under what conditions a spacetime that is initially
spatially anisotropic and/or inhomogeneous will flow into an isotropic and
homogeneous state. Wald's theorem, in particular, established that homogeneous
but anisotropic spacetimes, if filled with a positive cosmological constant
plus additional matter sources that satisfy specific energy conditions, will
necessarily flow toward an (isotropic) de Sitter state at late times. In this
paper we study the flow of homogeneous but anisotropic spacetimes toward
isotropic states under conditions more general than those to which Wald's
theorem applies. We construct an effective field theory (EFT) treatment for
generic ``single-clock" systems in anisotropic spacetimes -- which are not
limited to realizations compatible with scalar-field constructions -- and
identify fixed points in the resulting phase space. We identify regions of this
phase space that flow to isotropic fixed points -- including a de Sitter fixed
point -- even in the absence of a bare cosmological constant, and for matter
sources that do not obey the energy conditions required for Wald's theorem.
Such flows into de Sitter reveal the emergence of an effective cosmological
constant.
