So, l was wondering, are there any rules for who/what can act as a hexblade patron? I know the most common type of hexblade (based on what i've seen online) is "so, l found this magic sword, and it gave me superpowers!" type of hex blade (ie, the patron is also their weapon), but seeing as the hexblade subclass is meant to be a warlock who was given magic and a sword, as shown with a certian hajf orc who got his from a evil snee snake, l was wondering lf other things could make hexblades. For example, l want my current character to get power from a fiend (succubus), but l want to be a hexblade, not fiend pact. Would this be possable in lore? (Ie, is there a example in offical lore l could use as a example should the dm require one) 

From what I have gathered from the subclass, the Hexblade Patron is typically a powerful entity connected to the Shadowfell, an entity who can manifest their shadowy powers into weapons and gift their pact holders with the ability to cast shadowy hexes that leave targets vulnerable to their attacks. Powerful sentient weapons created from the essence of the Shadowfell are one option given for a patron. The Raven Queen is another. 

However, it is not too difficult to modify this to fit other types of entities. Using the succubus for example, your hexes could be flavored as your patron gifting you the ability to drain energy from those you curse much like how a succubus drains energy from those they are intimate with, strengthening you attacks and even healing you when you slay the cursed target. Your Accursed Spector ability could be that you force a creature to fall for you so strongly that they raise from the dead as a Spector with the desire to serve you. You can take invocations like ‘Mask of Many Faces’ to mimic the succubus‘s ability to transform into any desired form, and ‘Beguiling Influence’ to give you proficiency in Deception and Persuasion to fit with the idea of succubus being seductive and pleasing to listen too. 

Truthfully, it wouldn’t be that hard to flavor a Hexblade to be bound to a succubus.

So the official Hexblade write up says the Hexblade is a pact with something in the Shadowfell, sometimes presumed to always be the Raven Queen, but that's not definitive in the lore (though the Shadowfell origin is).  That said I don't see any reason why a Hexblade couldn't have some other planar origin, if you're DM is willing to work with you on the nature of that patron.  

Quote from RoughCoronet0 >>

You can take invocations like ‘Mask of Many Faces’ to mimic the succubus‘s ability to transform into any desired form, and ‘Beguiling Influence’ to give you proficiency in Deception and Persuasion to fit with the idea of succubus being seductive and pleasing to listen too.

 Great idea! Shame l already have all of those from being a changeling, lol. (though, rather then disguise self at will, l have alter self at will, which is a higher level EI)

I was in a game last year where we had a Changeling Hexblade who's patron was his weapon, but his weapon was a magical Mimic. The reveal that his mace was a Mimic was just... fantastic (specifically because it saved us from another mimic by courting the first one).

I have seen some different patrons for warlocks that don’t match any of the rules, for instance for a hex blade a powerful Fey who was an expert duelist, he wanted the player to become his equal so he could duel him.

A minor god who had become forgotten and forgotten who she was. Then one day the character had read a history book about this god while in the vicinity which had been enough to give this god enough power to be a patron. (Stolen from terry pratchet small gods) 

I’m looking to build a hexblade pact of the blade warlock dhampir but pacted to tiamat would this be possible 

That's a question for your DM. Generally speaking, Tiamat is more properly an Archfiend patron, being a denizen of the Lower Planes, but in terms of what vibes with the powers Hexblade is a fairly flexible Warlock patron, lore-wise.

So .. I realise this is stupid, but could a warlocks patron be, like, Joe Fighter? We'll assume Joe is legitimately 'otherworldly', like an eladrin or a teifling or some such. So, over beers sometime down at Grumblebeards Dwarven Alery, Tavern and Fighting Pit, our friendly (aspiring) warlock - let's call him Jim - get's talking to Joe. Jim explains that he want's to become a warlock, but none of the potential patrons will take him on. And so Joe asks:

"Well, what does patroning require?"

"A powerful, otherworldly being. Can you believe it? Like, that's literally in the job description. You'd think they could be a bit more specific, right?"

"Well .. um, I mean, I'm available. You seem cool - I'd take you on as my ... what would you be?"

"Well, I'd be sort of your agent .. wait, what am I even saying: You can't be me patron. How are you a powerful, otherworldly being?"

"Whaddaya mean? I'm way powerful. Look at these biceps *flex* - and I got this sword, and a shield. This neat armor. What say we try? If it works, it works. You do occasional favors for me, and I grant you powers. Ok?"

Is there anything in the rules that actually rules this out? 

Nothing strictly in RAW, but the implication from the examples given is that a patron needs a lot of power if they’re going to be able to pass on enough to potentially empower someone up to level 20. So no, generally speaking some random mortal fighter is not what’s intended as a patron.

As I understand the (admittedly confusing) subclass description, your patron is an intelligent weapon that is itself in service to some shadowy entity that may or may not be the Raven Queen. So you encounter a neat sword somewhere and the sword says, “hey, want to learn some magic tricks?” Notably this weapon is not your pact weapon (assuming you went Pact of the Blade because… c’mon).

Probably the closest analogue I can think of in popular media is: imagine the One Ring is your patron, but the Ring is a sword instead.

Having said all of that, I don’t think anyone really runs a hexblade the way it’s written because it’s weirdly specific and difficult to really envision. So… just work out however you want your spooky sword boi to work and go with it.

Quote from The_Ace_of_Rogues >>

Nothing strictly in RAW, but the implication from the examples given is that a patron needs a lot of power if they’re going to be able to pass on enough to potentially empower someone up to level 20. So no, generally speaking some random mortal fighter is not what’s intended as a patron.

 I'm aware it's not intended. But that doesn't mean that there's anything in RAW that rules it out.

while the RAW requirement is that it be somehow Shadowfell related, I can see at least 3 ways around that:

1) the shadowfell doesn't exist in the world you're adventuring in so the weapon could be from any very powerful "otherworldly" entity.
2) the weapon is from the Shadoqwfell but the entity is not - it could even be a good entity that wants to see the weapon used for good despite its origin.
3) the entity is not originally from the shadowfell but has extensive experience in the shadowfell and either acquired or created the weapon in the Shadowfell and is now offering it for an unkown (so far) reason.

I have a deity in my world that fits both 2 & 3 and might be willing to "spread the wealth" with stuff he has acquired in his extensive explorations of the shadowfell.

In my experience aberrations make great hexblade patrons. The shadowy powers of a hexblade could easily be worked around as clouds of entropy from a Star Spawn Emissary. Spells that are used in the warlock class could be reflavored  fairly easily too. I know that the warlock has the great old one patron but I feel that it doesn't have the luster or flexibility the hexblade has. An Idea I had for this was when I began reading the Eberron Campaign. Some of the Magic weapons are symbionts, Like Dyrrns tentacle whip or another weapon being Kinesthetic Projection or any mind flayer weapon for that matter. 

Hear me out. Strahd could make an awesome patron in CoS because maybe they already have connections to the vishtai and strahd gives you power as long as you are able to get the party to his castle for "dinner" and is working as a secret servant, so much potential there.

Ran a campaign where the Hexblade patron was the weapon of a fallen god embedded in the altar of a forgotten temple.  It imbued blades in the world with a portion of its power to test candidates to find someone worthy to find it and wield it..  This let me create a campaign -- find the temple, free the blade.  I also homebrewed the rules to allow the patron blade to imbue more power into its pact blades as the Hexblade character progressed.

Ya, Hexblades are really cool in concept, but the RAW description can be kinda restricting in terms of patron and backstory, so from what I've seen people just choose any patron that can potentially give you a magic weapon, sentient or not. I just started a CoS campaign playing a Hexblade drow that made a deal with one of the drow gods, but instead of being gifted the weapon was given a magical inclination for combat and fighting, since neither me or my DM wanted to deal with the sentient weapon schtick. Plus this still lines up mechanically and lore-wise since becoming a Hexblade immediately gives you proficiency in all weapons and light/medium armor and shields at level 1, and my patron is a also a warrior himself. 

Quote from TKDLinc >>

instead of being gifted the weapon was given a magical inclination for combat and fighting, since neither me or my DM wanted to deal with the sentient weapon schtick.

 That's actually the default fluff. Hexblade warlocks make a pact with a Shadowfell entity that is known for creating sentient weapons, but nowhere does it say that the warlock gets to wield one of those. The warlock gains proficiency with medium armor, shields and martial weapons, but they have to find such equipment themselves.