The Vampire Lord, also known as WzVAMP, is an enemy from the original Final Fantasy. It is found in the Flying Fortress and in floors F2, F3 and more commonly B4 of the Chaos Shrine. It is of no threat (as none of its spells or abilities can threaten a party appropriate-leveled for the Fortress).
The NES version has a bug that makes the Vampire Lord even easier. It casts AFIR (NulBlaze), but in the NES elemental protection spells don't work if the enemy that casts/gets affected by them is weak to the element it protects against. Vampires are weak against Fire, so AFIR will do nothing.
Vampires are mythological or folkloric beings who subsist by feeding on the life essence, generally in the form of blood, of living creatures. Although vampiric entities have been recorded in many cultures, and may go back to "prehistoric times", the term vampire was not popularized until the early 18th century.