Vial of Blood

The Vial of Blood summons a pet Bat when used. It grants the player the Pet Bat buff that lasts until the player manually cancels the buff or dies. The pet bat flies around the player, dealing 2-4 damage to enemies it happens to touch, and can travel through all blocks. When a player is in a body of water, the bat will fly above it like any other type of bat. When the pet bat gets too far from the player, it can fly back instead of shooting back with clouds behind it.

The Vial of Blood is an uncommon drop from Vampire Miners. It can also rarely be obtained from Golden Chests.

Trivia

 * The Pet Bat is the only Bat which can travel through blocks.