Sanguine Staff

The Sanguine Staff is a summon weapon dropped by Dreadnautilus. It summons a Sanguine Bat to fight for you. Sanguine Bat minions remain by the player's side until an enemy is in sight, and attack by flying in an elliptical loop between the player and enemy. They immediately return to the player's side once their target dies.

Trivia

 * Sanguine is latin for blood