Ophiel is the governour of such things as are attributed to Mercury.
His Spirits are 100000 Legions: he easily giveth Familiar Spirits: he teacheth all Arts: and he that is dignified with his Character, he maketh him to be able in amoment to convert Quicksilver into the Philosophers stone.
Arbatel of Magic, Robert Turner translation
This olympian spirit is associated with the astrological body Mercury
This olympian spirit provides the magic object Philosopher's Stone