The demon Baron appears in the grimoires The Grimoire of Arthur Gauntlet and The Book of Oberon
From Book of Oberon, Dan Harms edition:
Conjuration of Baron
Then say I charge thee thou spirit Baron as thou appearest unto me by this Conjuration and Invocation that thou shewe what is thy property to do without any dissimulation and whether thou be bound to any man or not before this time: and I charge thee to tell me if such a spirit N be bound to any man or not before this time and also I charge thee thou prince Baron which appearest unto me before this circle by the virtue of the most holy & dreadful names of God all which are graven in this scepter pentacle representing the strong pentacles of Salomon containing in it the foresaid dreadful names of God...
Gilles de Rais was accused of summoning this demon.