Age

Your aging slows to a halt. You are unable to age any further than the exact age you were when you became a vampire.

Unholy Power

Your STR becomes 18 unless it is already higher.
You gain +2 DEX and CON.
The sanguine curse is now so powerful it enhances ever aspect of your physicality, no prey can escape your unholy grasp.

Vampiric Nature

You are now considered both an undead and a humanoid. As an undead, you no longer need to breathe, you are immune to disease, and you are resistant to necrotic damage. However, due to your unholy nature, you are vulnerable to radiant damage.

Darkvision

Accustomed to hunting at night, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray. If you already had Darkvision when you got this feat, add 60 feet onto it.

Blood Hunger

You have a Blood craving to satisfy.  You must feed, taking at least one vial, or 4 ounces, of blood, into yourself every 48 hours, or begin to take levels of exhaustion. While that is just enough to sustain you, you still feel the urge to drink and may still appear twitchy or ravenous in the heat of battle or when treating a wounded ally. A pint, such as that contained within a flask is considered a healthy amount, enough to keep you sustained while also suppressing your less civilized behavior.

Blood Thirst

You can drain blood and life energy from a willing creature, or one that is Grappled by you, Incapacitated, or Restrained. If an unwilling creature bitten this way is able to successfully escape restraint, grappling, or incapacity the effect ends. An unwilling creature must make a Constitution saving throw, the DC for this saving throw is 18.
An Unconscious creature automatically fails.

A creature takes 2d6+STR/or/DEX necrotic damage per turn on a failed save, and half as much damage on a successful one. Using Blood Thirst also allows you to drink the blood from your victim, giving you 4 ounces of blood. For the purposes of collection, a "Vial, potion, or bottle" can be used. How much a container can contain is DM discretion.  Additionally you may choose not to deal any damage when biting a sleeping or willing creature. Each creature you bite without dealing damage must finish a long rest before you can do so again.

The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

The damage increases to 3d6 at 5th level, 5d6 at 11th level, and 6d6 at 17th level.
The number of uses increases at 7th level.

Advanced Regeneration

You regain 1d6 Hit Points every round, provided that you have at least 1 hit point. If you lose a body part, you can have the missing part regrow and return to full functionality after a long rest if you have at least 1 hit point the whole time. Hit die are no longer needed, you heal to full on a short rest. If you die, you come back to life in 10 minutes assuming you are not decapitated, staked through the heart, or have blood hunger. Your exhaustion is set to 1 regardless of what it was when you died and you gain blood hunger.

Shapechanger

You can use your action to Polymorph into a Tiny bat or a Medium cloud of mist, or back into your true form.
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 size and speed, are unchanged. Anything you are wearing transforms with you, but nothing you're carrying does. You revert to your true form if you die.
While in mist form, the vampire can't take any Actions, speak, or manipulate Objects. It is weightless, has a flying speed of 20 feet, can hover, and can enter a Hostile creature's space and stop there. In addition, if air can pass through a space, the mist can do so without squeezing, and it can't pass through water. It has advantage on Strength, Dexterity, and Constitution Saving Throws, and it is immune to all nonmagical damage