Your patron is a vampire that has lived so long and amassed so much power, they have plenty to spare. In exchange for your service, this ageless creature imbues you with a modicum of it's own power via a pact made in blood. You receive a number of dark gifts (and a few weaknesses) synonymous with vampires, without the inconvenience of dying. 

Expanded Spell List

The Ancient Vampire lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Ancient Vampire Expanded Spells

Spell Level	Spells
1st	feather fall, hunter's mark
2nd	detect thoughts, pass without trace
3rd	blink, haste
4th	dominate beast, locate creature
5th	dominate person, mislead

Red Shift

Starting at 1st level, you begin a quasi-vampiric transformation.

Tooth and Claw. You can grow pronounced fangs and claws at will. As an action, you can use them as natural weapons that do 1d6 + your charisma modifier of piercing (bite) or slashing (claws) damage. If the target is a willing, surprised, grappled, incapacitated, or restrained creature, you may feed on their blood and gain temporary hit points equal to the bite damage dealt. (The temporary hit points gained cannot exceed the target creature's current hit points) You cannot feed from an undead creature or a construct. Once you have fed, you cannot use your feeding feature again until you complete a long rest. As your warlock level increases, the damage die for your fangs and claws increase. At 6th level they increase by 1d6 ( making them 2d6). At 10th level your fangs and claws count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage. At 14th level the damage increases by an additional 1d6 (3d6 in total). 

At Warlock level 10, your reflexes quicken and your bite goes from an action to a bonus action. 

Strength of Blood. You may use your CHA modifier instead of STR for (Athletics) checks and when calculating jump distance. (Use stat skill override on the D&D Beyond character sheet)

Sunlight Sensitivity. While in sunlight, you have disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Hunter's senses. You have advantage on Wisdom (Perception) checks that rely on hearing and smell. And you can easily (no skill check required) pick up the scent of any spilled blood that is no older than 2 weeks within 100 feet of you.

Shapeshifting

Starting at level 6, when not in sunlight, you can use your action to polymorph into a Tiny bat. While in bat form, you can't speak, your walking speed is 5 feet, and you have a flying speed of 30 feet. Your statistics, other than your size and speed, are unchanged. Anything you are wearing but not things you are carrying in your hands transforms with you. You can stay transformed for a number of hours equal to half your warlock level (rounded down).You revert back to your true form when that time is expended, if your HP is 0 or you can willingly revert back as an action.

Once you've used this feature twice, you can’t use it again until you finish a long rest.

Touch of Undeath

Starting at 10th level, you no longer require food or water to sustain yourself. You age at a fraction of your normal rate and you are immune to the effects of magical aging.
You gain resistance to necrotic and cold damage but you are now vulnerable to radiant damage. When your hit points fall to zero, you may add your charisma modifier to your death saving throws. While rolling your death saves, if even a drop of fresh humanoid blood (Exposed to air for no longer than 30 minutes. Cannot be your own blood.) is put in your mouth you are restored to 1 hit point. Once you regain 1 hit point in this way, you cannot do so again until you complete a long rest.

Your reflexes quicken and your bite goes from an action to a bonus action. 

Your ability to shapeshift improves. You can now choose to polymorph into a swarm of bats

While within 30 feet of a holy symbol that you can see that is being wielded or worn by a person of faith, or when attempting to enter a church, temple, or other sacred or hallowed place, you must succeed in charisma save (DC 10+your warlock level) or become frightened. If you succeed, you cannot be frightened by that specific symbol or hallowed place for 24 hours. If you fail, you remain frightened for as long as you are within 30 feet of the source of your fear, and cannot attempt another wisdom save against that source for 24 hours.

Dark Evolution

At 14th level, your ability to shapeshift improves even further, allowing you to use this feature 4 times per long rest.You can now choose to polymorph into a humanoid/bat hybrid form, sprouting a pair of bat wings from your back that grant you a flying speed of 60ft. While in this form, you can speak, cast spells, and use your fang and claw attacks as normal. You also gain blindsight out to 60ft (Based on echolocation and cannot be used while deafened.). Your size and other stats remain the same as your base form.

You can now choose to feed from a fang attack and gain temporary hit points once per short rest. If your bite damage reduces the target's hit points to zero and it dies as a result, you may choose to forgo the temporary hit points and instead gain the benefits of a short rest. Once you use this feature in this way, you cannot feed again until after a completing a long rest.

You are now immune to the poison damage and disease.