Vampire

Vampires are Hardmode enemies that spawn only during a Solar Eclipse, during which they are about as common as a Zombie. Vampires 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 deal large amounts of damage, one of the highest amounts in the Eclipse.

Tips

 * Due to low lighting during a Solar Eclipse, it may be difficult to see this enemy before they strike you. Vampires in Terraria typically fly in as a bat which is relatively hard to see without artificial lighting. Therefore, using a Hunter Potion is recommended. Alternatively, try using light buffs (Shine Potion, Wisp in a Bottle) and watch for them as they fly in to prevent unnecessary damage.
 * The Stake Launcher is a highly effective weapon against Vampires, as it deals greatly increased damage to them.

Trivia

 * The theme of almost all of the Solar Eclipse enemies is classic horror film icons. Vampires are a reference to the 1931 film "Dracula,"
 * Being vulnerable to the Stake Launcher is obviously rooted in Vampire mythology/culture, where stakes are the usual method of destroying vampires.
 * 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.

History
Vampire Вампир