Seeking Information on the Eldritch Blades.

Thank you both for that clarification. Too many organizations like the term, I suppose.
How does the demon Malvazad tie into all of this? Wasn't that the being the Coven made their pact with?

Yes. The oldest brother, Embrose, convinced his siblings to make a pact with Malvazad. Both living siblings have been fully exorcized of his influence.