Vampirism

At night, or in a dark lit area the player is given advantage on all skill checks and saving throws based on Strength, Dexterity, Charisma, and Constitution. In areas with sunlight the player has disadvantage on all skill checks and saving throws based on Strength, Dexterity, Charisma, Constitution. In addition, the player has more of a ghoulish appearance during the day, and is considered undead at night. You become vulnerable to fire and radiant damage, and gain resistance to necrotic damage. 

Regeneration. At night, the creature gains resistance to bludgeoning, slashing, and piercing damage from non-magical weapons.

Restricted Healer. The creature can not be healed by healing potions. Additionally they can not be healed by divine magic. 

Feeding Habits. After one full day without feeding the creature must succeed a dc 12 Constitution saving throw or become feral. After the second full day without feeding the creature must succeed a dc 14 Constitution saving throw. After the second full day, the creature's ghoulish appearance become more prominent, and people will more likely become more hostile to them. You then loose your disadvantage on Strength and Dexterity skill checks and saving throws, the creature also gains their regeneration during the day. After the third full day without feeding the creature must succeed on dc 16 Constitution saving throw to prevent becoming feral. If the creature goes through a  full fourth day, the creature automatically becomes feral. Whenever the creature becomes feral, the creature attacks the closest person they see that has blood with intent to feed.

Action.

Blood Transfer. As an action, the vampire may choose to give or take 4 (1d6) hit points to another creature of it's choosing that contains blood. Any non-willing creature must succeed on a dc 15 Dexterity saving throw. When the vampire steals hit points, the creature the vampire stole the hit points from receives damage equivalent to the hit points taken. When the vampire gives another player these hit points, the vampire takes damage equivalent the hit points given. Additionally, The other creature taking/receiving the hit points must make a dc 14 Constitution saving throw, and if it's failed that creature contracts vampirism. If the vampire does this action on an unconscious creature, the creature fails both it's Dexterity and Constitution saving throws.