At 1st level you can use a leeching bite which does 1d6 damage and heals 1d4 - 1.

At 3rd level you gain the ability Vampiric Ancestry which allows you to choose to have resistance to either necrotic, or Fire damage.

At 7th level you can use a bonus action to become a bat and use the bat stat block for 1 minute. {once per long rest}

At all levels if you have a humanoids blood for that day you gain advantage on constitution checks.

You have Vulnerability to necrotic.

If in holy water, you take 1d20 damage per minute inside of the holy water.