The Monster Man that Gordon fights at Ethel Peabody's apartment is possibly a reference to the Man Bat from the Batman comics given his bat-like wings that we see in the photo Valerie Vale takes.
Reporter Valerie Vale is the aunt of recurring DC comics character and Bruce Wayne love interest, reporter Vicki Vale.
The episode title is the first half of a quote from John Milton's poem "Paradise Lost". The full line is "Better to reign in hell, than serve in heaven", and is how Satan describes himself.
Valerie Vale is driving an old Volvo P1800, which was the car driven by Simon Templar in The Saint. Its final model year of production was ~ 1973.
The club that Barbara and Tabatha own is called Sirens. This is a nod to the DC comic book Gotham City Sirens.