A proponent of panpsychism argues moral truth is inherent in consciousness

If an evil person were to become a god and decided to make a reality where moral intuition justified their depravities, surely we'd say that this was a perversion of moral sense rather than a different set of moral laws?

I think if morality varies between realities then we're just talking about preferences. This is why Plato held gods/God cannot simply make something Good because they command it.

Whatever the Good might be, like mathematics Its truth would have to be Universal.

In my view there must be an intelligent source that is the origin of even the Universals (otherwise the Universals are complex specified information of a high order that either always existed (a watch without  a watchmaker), or these Universals came into being from absolutely nothing (but nothing can come from absolutely nothing - absolutely nothing is not even space and time and laws of physics and laws of logic). This intelligent source may also be the origin of the much greater amount of complex specified information constituting the physics laws of the physical universe and all of its matter and energy, and of the spiritual order.  Or the origin of the physical universe and the spiritual order could be subsidiary powerful spiritual entities created by the central Cause. In all these cases there would be a single Universal moral ground. Some aberrant immoral god establishing an aberrant evil morality would be an impossibility - an untenable thought experiment.