Mechanical Leash of Cthulhu
The Mechanical Leash of Cthulhu is a craftable Hardmode flail. It fires a few mechanical Servant of Cthulhu projectiles while retracting, that home in on enemies to attack them. Upon directly hitting the enemy, it spawns a large amount of mechanical servants around the enemy.
As it is a 'launched' flail rather than a 'thrown' one, it cannot be flailed around as you walk, immediately disappearing upon its return.
Its best modifier is Godly.