What named creatures or beings would fit thematically as patrons of a Dark Pact warlock?

Question

What named creatures or beings would fit thematically as patrons of a Dark Pact warlock? By "named", I mean a being that exists in some lore (primarily but not necessarily limited to Forgotten Realms lore).

The only example I have seen is in the Dragon Magazine #381, where it lists (on page 48) a creature called Yorgrix, Weaver of the Poison Web, which is a demonweb spider living in the Underdark.

Before almost an entire page about that patron, it more broadly references this (also on page 48):

Whether drow, dark spirit, or creatures of terror, dark patrons lurk in the hidden places of the world.
    Common Patrons: Demons (especially servants to Lolth), purple dragons, and legendary dark spirits of the Underdark such as Yorgrix

So possible named patrons would presumably include any known Demon Lord (or any named demon), and any named purple dragon, but "legendary dark spirits" is a bit more vague...

The sentence above that mentions "drow, dark spirit, or creature of terror", so does that mean a drow mage would make an appropriate patron, kind of like a Sorcerer-King Pact (as I understand it)? This is more of a secondary question, though; my main question is about named beings that would work as patrons for a Dark Pact warlock.

Are there any other named examples throughout 4e source material? These "legendary dark spirits" are of primary interest to me, but I'm not really as interested in gathering lists of named demons or purple dragons (that sounds easier to simply Google, but expanding on what these "dark spirits" are is something I feel would benefit from 4e expertise; note that I only have knowledge of 5e).

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Related: What books cover Star Pact Warlocks and their awful masters?
Related: What books cover Fey Pact Warlocks and their awesome masters?

Answer 1

Unfortunately, aside from the Dragon issue that you mention, there are no real sources of lore on the Dark Pact for Warlocks. As much as I love 4e, I will admit that its early materials could often be relatively lore-sparse, and Dark Pact Warlocks suffer from only getting to be in two books; the Forgotten Realms Player's Guide where they debuted, and an assortment of new spells plus a devoted Paragon Path in Arcane Power. And unfortunately, despite the abundance of flavorful sidebars in that book, it doesn't devote any to discussing warlock patrons in more detail. The Dark Reckoner, the Dark Pact PP from that book, does mention that Dark patrons "tend to be consumed by vengeance".

That said, Heroes of Shadow does feature the Gloom Pact for Binders, a Warlock subclass built to the Essentials subrules. Aside from being tied to the Shadowfell, it's fundamentally just an Essentials reiteration of the Dark Pact. So you could justify a Dark Pact warlock using the same patrons, which are described as including Darklords, sorrowsworn (not the same as 5e's Silent Hill-esque monsters; 4e sorrowsworn are basically powerful psychopomps), nightwalkers (incredibly powerful "living shadow" type undead), fallen gods, "dark figures from time forgotten", and the Raven Queen herself.