Vampires are Hardmodeenemies that spawn only during a Solar Eclipse. They will turn into a bat if the player is above them and attempt to fly near the player and turn back into a humanoid. They can inflict the Bleeding debuff and are one of the most damaging enemies in Solar Eclipse.
Due to low lighting during a Solar Eclipse and the small size of the Vampire in its bat form, it may be difficult to see before it strikes the player. Therefore, using a Hunter Potion and artificial lighting (including buffs like Wisp in a Bottle or the effect of the Shine Potion) is recommended.
On the 3DS version, a Vampire can keep up with/outrun a player with Hermes Boots, even when it is not in its bat form.
The theme of almost all of the Solar Eclipse enemies is classic horror film icons. Vampires are a reference to the 1931 American vampire-horror film Dracula.
The Stake Launcher's damage bonus references real-life vampire folklore, in which the only way to completely kill a vampire is to drive a wooden stake through its heart.
Vampires in modern fiction are often said to be vulnerable to sunlight. While Vampires in Terraria do attempt to flee during the day when the Solar Eclipse is over, like all other enemies, they do not actually take damage from the sun.
Sand Sharks use the Vampire's idle audio as a jump noise.
The Bestiary entry for the Vampire: "Whether he is a man who turns into a bat, or a bat who turns into a man, one thing is for sure: he's out for blood!"