This lecture will have less structure and will cover the mechanics of the operations contained with Ars Goetia, Grimorium Verum, and Abramelin the Mage. As such, I will split the lecture into three parts, one for each grimoire. These are extremely bare-bones renditions of how each grimoire lays out its operations, so some technicals may not show up.
Generally speaking, “invocation” entails a “calling in” — for example, in the Golden Dawn’s Lesser Banishing Ritual of the Pentagram, one invokes the four archangels to come down and protect the operator.
“Evocation” is a “calling forth.”
In general, one invokes a safe entity, such as an angel, who in turn acts as a go-between for the sorcerer and the demonic entities one seeks to summon.