Muito pouco, embora alguns tenham conexões com ele.

Dos patronos do Grande Velho listados no Manual do Jogador e Guia do Aventureiro da Costa da Espada, nenhum tem um sólido interesse na Guerra do Sangue.

De acordo com a Elder Evils (2007) Zargon foi governante dos Nove Infernos nos tempos antigos, antes de ser expulso por Asmodeus. No entanto, após seu exílio no Plano Material, ele já desistiu de seus planos de retornar aos Nove Infernos, decidindo tomar o Plano Material:

The slime bred new creatures that Zargon sought to corral and use as foot soldiers to reclaim his place in the Nine Hells. But as his power grew, Zargon realized this world could be his. He had no reason to return to his native plane when he could claim this one.

Nos Reinos Esquecidos, Moander, listado como o Grande Antigo no Guia do Aventureiro da Costa da Espada, na verdade residia na camada 223rd do abismo, Offalmound. No entanto, Moander foi morto e, de acordo com Guia do jogador para Faerûn p.165, isso fez com que seu reino fosse destruído ou expulso dos aviões, o que significa que Moander não tem mais participação direta na Guerra do Sangue.

Kezef Chaos Hound, um dos sete deuses perdidos de acordo com o Guia de Campanha Forgotten Realms (2008), caça muitas divindades, mas não tem nenhuma conexão particular com a Guerra do Sangue.

Dendar A Serpente da Noite, também um dos Sete Deuses Perdidos, é dito em Poderes e Panteões (1997), p. 188, para ser um antigo mal dos anciões, sinônimo do mito Nidhogg of Norse, o dragão que roe a árvore do mundo Yggdrasil. Ela habita o Desperdício Cinzento de Hades, que é usado como um campo de batalha da Guerra do Sangue, mas Dendar geralmente não deixa seu covil, contente em se deliciar com os pesadelos dos mortais, e não tem nenhum interesse particular na Guerra do Sangue que se enfurece fora dela. caverna.

Ghaunadaur é inimiga de Lolth, cujo reino o Demonweb Pits era uma camada do Abismo, mas pela linha do tempo atual dos Forgotten Realms, seu reino é separado do Abismo. Ele agora ocupa um plano separado chamado Cavernas Sombrias ou Cavernas Profundas, e não tem conexões conhecidas com a Guerra do Sangue.

Tyranthraxus possui corpos mortais no Plano Material e deseja conquistar Faerûn, mas não tem conexões conhecidas com a Guerra do Sangue. De acordo com Maldição dos títulos Azure, his origin is unknown and "none of the lower planes will claim him".

Tharizdun of the Greyhawk lore is an ancient entity of utter bleakness and annihilation, imprisoned by the gods to prevent him from destroying the entire multiverse. He has no connection to the Blood War. He may have a tangential connection via the Elder Elemental Eye, a proxy identity under which he was revered in the Templo do Mal Elemental, and which brought together the power of evil elemental princes who may themselves have some small stake in the Blood War.

Great Cthulhu was omitted from most D&D books for copyright reasons, so there is unlikely to be lore connecting him to the Blood War. Traditionally, he sleeps in his forgotten city beneath the oceans.

O Manual do Jogador ends its list with "other unfathomable beings", which suggests that some other Great Old One patrons might exist who care about the Blood War. However, they are described in the Manual do Jogador as having motives "incomprehensible to mortals", and the general trend is that Great Old Ones tend to be bizarre entities even older than the war between demons and devils.

Yes, and no. But really, you probably should not know!

If you want to embrace the full spirit of the Great Old Ones, we cannot know. They might be interested, but for reasons we cannot fathom. The established D&D lore, from 3.5e books like Elder Evils, but better yet Senhores da Loucura, does not establish much of a connection, but perhaps the fact that we are unable to see the connection is an illusion, perhaps they are interested but we are unable to comprehend the connection. As soon as you fully flesh out the reason why a certain Great Old One would be interested in the Blood War, you are making it understandable by mortals.

So I suggest: Do not try to find any connections at all. If this is not satisfactory, ie. you want to establish a solvable mystery, do not flesh out the connection yourself, just state your desire to your DM and let her establish one so you won't know. It will make roleplaying your character more exciting, you as the player won't need to pretend unknowing what your character should not know. But even as the adventure unfolds and you start to gain clues about what your DM has prepared, you should not be able to completely understand the full picture; some clues should even be contradictory; ideally as soon as you start to think you are grasping the big picture, some new clue must totally ruin it.

Most of us want to have a big comprehensible picture. If the lack of it would make your character less fun to play, please also state that to your DM, so she can adjust the level of mystery accordingly.

Now some loose threads that might inspire your DM:

All of the following information comes from various pages of the Lords of Madness.

1. Quoting: "Of all the major aberration races in the D&D game, the aboleths best personify the sense of cosmic horror and the ultimate insignificance of humankind expressed in Lovecraft’s writings."

2. Eons ago, exceptionally gargantuan aboleths managed to transport an entire world of slaves and minions from the Material Plane to Stygia, the icy-cold ocean layer of Nine Hells.

3. Aboleths in general like interacting with the baatezu, and collect means of summoning and binding them to servitude.

4. Piscaethces, the source of the aboleth race, could be the alternate name for Cthulhu or Shub-Niggurath from the Lovecraftian mythos.

5. While Piscaethces does not seem to care about the aboleths or any other beings in the physical world, insane cultists periodically attempt to call her.

Work with your DM

This fantastic answer goes through a pretty exhaustive list of GOO patrons and how they'd feel about the Blood War. It's pretty clear that there aren't any GOO that would have a direct, vested interest in the Blood War itself. However, it's very possible for a DM to work a clear, cohesive hook in for you if that's what you want to play.

For a related example, I was playing an Undying Warlock through Curse of Strahd. There wasn't really a good reason for my patron (a mega-lich from a previous campaign) to care about Ravenloft on its own. However, the DM gave me a great hook: My Patron sent me to Ravenloft to find out how Strahd gained his powers, and seize the source of his dark magic for my patron (or at minimum learn everything around it). This meant that I had a solid reason for being there, but it was very different than the rest of the party. Our goals aligned for most of the campaign except for (CoS spoilers):

When we reached the Amber Temple, I had to do some really tricky roleplaying while trying to learn everything I could about the vestiges. The party didn't know about my secret motivation, so I had to think fast to figure out reasons why I was obsessively studying each of the vestiges and what gifts they offered. I had similar fun RP when we found Strahd's journal and I had to secretly steal it for my patron.

Although your patron may not be interested in the whole blood war, they don't need to be for you to play in this campaign. They really only need an express interest in one or two major players, or in a major artifact involved in the campaign, or some kind of lore or knowledge involved in the campaign. I haven't read Descent into Avernus yet, but it's entirely possible that one of the Fiends involved knows some secret that your patron wants, or has a powerful artifact that the patron wants. Your DM should be able to figure out something that would hook you into the campaign with the party, and that would reasonably advance your patron's goals in the world. This kind of situation can lead to some really fun and challenging RP and character choices too, so I'd highly recommend it.