Sunfury

The Sunfury is a rare drop flail category weapon from Bone Serpents in The Underworld. It's an orange flail that emits light during attack and deals 40 points of damage, but can hit multiple enemies at once and one enemy twice (or multiple times in the case of a boss). The Sunfury has a 1/100 chance to drop from Bone Serpent.

When the ball goes too far from the player or hits a block, it quickly retracts. Like boomerangs and other flails, throwing the weapon behind a line of enemies will force it to retract through them all, dealing damage to every one of them. This is especially effective in dealing with Goblins.

Below is a video looking at the Sunfury:

How to farm a sunfury: