Orcus is the planet I think of merciless Scepticism, the unwillingness to take anything on face value, the question and challenge everything.
Orcus is a deeply Rational planet, it scorns the Emotional and what does not answer criticisms.
Orcus is the natural enemy of pseudo-science and superstition of all sorts. Orcus has faith in nothing and tests everything, everything is guilty unless proven innocent, negative unless proven positive.
Orcus believes only in what proves too strong to tear down, ultimately Orcus leads to ultra-scepticism, the unwillingness to accept anything whatsoever as definate.