i was thinking of making that an sheath of an int weapon that one of the first paladins of my oath wielded but it got corrupted (i whanted to name my patron avalon )
Generally speaking a Hexblade Warlock does not wield their patron, their patron is not their tool, it is their master, If you're wanting to be lore compliant. If you are looking to be lore compliant then Oath of Conquest generally works best for Hexblade for multiple reasons but the easiest is swearing an oath in service too the Raven Queen (thus conquest or crown works well), since most hexblade patrons generally serve the Raven Queen.
What might work is if the weapon is a fake, designed to look identical too the original but is really a weapon of the shadowfell and that it is deceiving various people into doing it's various deeds but even then, it probably wouldn't grant itself to be used as a weapon. There are also other limitations regarding sentient weapons and pact weapons, in that a sentient weapon can not be a pact weapon: https://www.sageadvice.eu/clarify-blade-pact-cant-make-sentient-weapon-a-pact-weapon/
You could still make a sentient weapon a hex weapon (as per hex warrior) but you'll never be able to benefit from Pact of the Blade for it, depending on how high you intend to go into warlock that could prove to be an issue later on, for a single level dip it isn't an issue at all but if you intend to go Paladin 15/warlock 5 or Paladin 11/Warlock 9, it could cause build issues as you'd miss out on invocations like Improved Pact Weapon (ability to use your weapon as a warlock spellcasting focus can be nice if holding a shield in the other hand) or Eldritch Smite.
Overall, you'd need to work with your DM on the details, the paladin/hexblade combo has always been strong but a hard one to justify on the lore front.
Personally when I made a paladin(devotion)/hexblade I did not go entirely lore compliant, instead I came up with a backstory that a bunch of cultists tried to sacrifice my paladin in the past but Bahamut stepped in to try and protect his loyal follower, in the ensuing tug of war her soul got split in two, the part dedicated to Bahamut remained while the other half was split off. When she got reunited with the missing half of her soul, it had been altered and changed into becoming a weapon. Both look to be reunited but in different ways, the paladin wanting to get her soul fully back in her body while the weapon wants the soul fully in the weapon, since both want the other alive until they can achieve their goals, they are working together but fundamentally also against each other. It's not entirely lore compliant but I think it works well enough and ultimately it's about what your DM is willing to work with, thus best option is always work with your DM.
i was thinking of making that an sheath of an int weapon that one of the first paladins of my oath wielded but it got corrupted (i whanted to name my patron avalon )
Generally speaking a Hexblade Warlock does not wield their patron, their patron is not their tool, it is their master, If you're wanting to be lore compliant. If you are looking to be lore compliant then Oath of Conquest generally works best for Hexblade for multiple reasons but the easiest is swearing an oath in service too the Raven Queen (thus conquest or crown works well), since most hexblade patrons generally serve the Raven Queen.
What might work is if the weapon is a fake, designed to look identical too the original but is really a weapon of the shadowfell and that it is deceiving various people into doing it's various deeds but even then, it probably wouldn't grant itself to be used as a weapon. There are also other limitations regarding sentient weapons and pact weapons, in that a sentient weapon can not be a pact weapon: https://www.sageadvice.eu/clarify-blade-pact-cant-make-sentient-weapon-a-pact-weapon/
You could still make a sentient weapon a hex weapon (as per hex warrior) but you'll never be able to benefit from Pact of the Blade for it, depending on how high you intend to go into warlock that could prove to be an issue later on, for a single level dip it isn't an issue at all but if you intend to go Paladin 15/warlock 5 or Paladin 11/Warlock 9, it could cause build issues as you'd miss out on invocations like Improved Pact Weapon (ability to use your weapon as a warlock spellcasting focus can be nice if holding a shield in the other hand) or Eldritch Smite.
Overall, you'd need to work with your DM on the details, the paladin/hexblade combo has always been strong but a hard one to justify on the lore front.
Personally when I made a paladin(devotion)/hexblade I did not go entirely lore compliant, instead I came up with a backstory that a bunch of cultists tried to sacrifice my paladin in the past but Bahamut stepped in to try and protect his loyal follower, in the ensuing tug of war her soul got split in two, the part dedicated to Bahamut remained while the other half was split off. When she got reunited with the missing half of her soul, it had been altered and changed into becoming a weapon. Both look to be reunited but in different ways, the paladin wanting to get her soul fully back in her body while the weapon wants the soul fully in the weapon, since both want the other alive until they can achieve their goals, they are working together but fundamentally also against each other. It's not entirely lore compliant but I think it works well enough and ultimately it's about what your DM is willing to work with, thus best option is always work with your DM.