So I'm going to be DMing for a group of friends who have never played D&D before, and I've made a few tweaks to make things fun for them all, and help focus on the story aspect of everything, one of my players (was so proud of him for his decision) choose to play a Tiefling Hexblade, and I asked him if he wanted to create a patron in his backstory or if he wanted it to develop over the story, he said develop. I've know this guy for nearly all my life, and he loves Spider-Man, so I was kinda thinking of giving him a Spider-Demon patron, I've already thought up of how he'll be hinted that his patron is a spider demon thing. But I'm not sure what to base it off of? Like a part of me is wanting to base it heavily off The Other from Marvel Comics, but I'm not sure I want that route since it might include possession and I do want him to enjoy his first character. If anyone has any thoughts on how I can build this up I'd love to hear them.
Well since the Raven Queen doesn't have any connection to spiders, I would say you have three options:
1. Have a spider themed sentient item that is guiding your player to find it. This would fit the current lore of Hexblades better since it can be implied that they get their powers from sentient items instead of from the Raven Queen. You would need to make a sentient item for them to acquire, which you would also need to balance with the other players rewards as well. You could also go the awaken/legacy path of sentient items and have him start with it, but all it does is talk them and act as their patron. As they level you can introduce story arcs that will unlock abilities of the item which will improve it's power.
2. Modify the lore behind the Hexblade to better fit a Spider theme patron, it doesn't have to be a demon. It could always be a Fey spirit that happens to be a Spider. If you go this route you could tweak the Hexblade to better fit the new lore ability wise. Like replace one of the expanded 2nd level spells with Web. Maybe also bring in the aspect of weaving fate and stuff like that.
3. There are plenty of Homebrew Patrons that would better fit the theme your trying to go with, that is if a non-Hexblade Patron is a option. Here is one possibility from a site I found awhile ago for another Warlock Patron.
If you really wanted, you could make it some sort of otherworldly spider being trapped inside a weapon. Say hundreds of years ago there was a group of adventurers that sealed it away into the blade, and it’s attempting to be freed by influencing mortals. Maybe if he finds the weapon that it’s trapped in (late into the campaign), you can have him roll wisdom saving throws in order to resist the influence, or he might decide to straight up free his patron of his own accord in order to garner its favor.
I actually really like that idea, because the world and mechanic I'm using for them are homebrewed, and I'm trying to do something similar to Matthew Mercer creating the patron for Fjord. Otherworldly Spider creature could work really well, as long as there's still the chance it can call out to his character, and communicate with him. I sorta had an idea of having him needing to search for 8 weapons, each representing a piece of his patron, and when he's collect them all, I'm wondering if there's something special I could give him.
Maybe if he collects all eight pieces he ends up like that iron man/spider-man suit. Except like with the venom color scheme or something. Or maybe they come together to form an even more powerful weapon that has a special effect.
You could always have their Patron be an Item that was created by Lolth herself, that was then then secreted away to the the Shadowfell long after it was lost and forgotten by the Drow. The Raven Queen wants to keep it hidden from the planes and It simply wants to be returned to the Underdark. It would probably be old and powerful enough to grant power to your friend power to try to meet it's own ends.
You could also simply re-flavor some of the standard spells and Invocations for warlocks to be Spider themed stuff, Arms\Hunger of Hadar and Shadow of Moil are no longer tentacles in darkness but arachnid legs in a pool of dark sticky polymer-fluids, his Eldritch blast is now poison based and if he takes the Grasp of Hadar invocation it reels them closer to him with visible white shimmering white lines and such. Push him towards spells like Blight, Vampiric touch, Infestation, etc.
If he wants a spider Patron, just tweak the Aesthetics about like Matt Mercer does.
Hexblades Curse and Hex? Wraps that targets body in ethereal gossamer threads leading to the Hexblades weapon, flavor its like they're being reeled into the blade. Or maybe there Eldritch blasts travel through the threads to strike the target.
Accursed Specter? Re flavor it so that when a humanoid is killed, a Specter doesn't appear, but rather a Phase spider burst out of there corpse (Still mechanically treat it as Specter thought). It helps avoid the moral quandaries of creating undead, and plays into the creepy miss conception of spiders bursting out of wounds.
Eldritch Sight Invocation ? Make it so that they grow additonal Spider eyes when they need to see magic.
As for the nature of the patron, ask your Player what they want? If they want to lean into the demonic angle of things, Looking at Phantasmaraneae from Bayonetta.
If they want to go for something mysterious beautiful and Feylike, Make it a giant peacock spider that wants they Teifling as a memeber of there court. After all, a bunch of tropical spiders species form complex Social colonies where they work in group and develop communal webs. Or you can do the same exact thing and flavor it as an elder evil trying to take the Hexblade as a unit of a hive mind.
Hell, wolf spiders even care for there young, and will sooth them when they sense thier brood is stressed out. Make an Ophanim Celestial (the ones that look likes wheels) that takes the form of a Wheel Spider.