Psohdon

Psohdon is a spirit from Der Kloster, referenced in the Dictionary of Occult, Hermetic and Alchemical Sigils. Der Kloster is an out-of-print German book written in an unscannable font, so the actual properties of this spirit are as of yet unknown. Psohdon also appears in the Standard Set with the title "The Inconstant". It's very likely that this is an alternate name for Poseidon.