I'm making a Dhampir Human Vengeance Paladin who was once a governess of a royal school of magic, but then the school was taken over by a royal family who turned out to be a necromancer cult with a vampire priest as the new headmaster. When she defied their orders the headmaster turned her into his personal slave and hunter of other traitors. After years of submission, she finally broke free. She ran as far as she could, until she came upon a temple. The priest, familiar with the curse, took her in. They taught her to control the dark urges and to use her curse for the greater good, in hopes that some day she can be redeemed. She now hunts the wicked and unholy, while also fighting the inner darkness within herself. And some day she'll come back home to confront the evil that took her life from her. Her name is Nina Amberstone.

I'm not sure which deity I'm going to choose since we're playing in Eberron. I'm also making her a Dexterity based paladin. I was kind of thinking about creating a Batman/V for Vendetta character where she tracks the evil to Sharn's corrupt underbelly.

Keep in mind that vampiric bite is a Constitution attack (including bonuses) and that hunter's mark (you get it at lev3) increases it's (piercing) damage (f use with HP or skills checks) but Divine Smite is radiant damage....so you can do it with a bite, but you don't get the Divine Smite damage for healing or ability checks through the bite.