Thunder Zapper

It only appears in the sandstone chests placed well down in the Underground Desert, which is a rough biome to be in at the point where you would want this. There is a useful tell. If the chest you just cracked had a Storm Spear or a Bast Statue as its headline item, you are already deep enough for the Zapper to be in the pool. If it had anything else, you need to keep going down.

Fishing the Oasis is the calmer route if you can set it up, since the crates roll the same item without the tomb crawlers in your face. Remix worlds move the chests to a much safer spot below the desert walls.

The shot weaves left and right as it travels rather than flying straight, then fizzles out after about a second or on the first thing it touches. It does not pierce, so every bolt is worth exactly one target. What it has instead is a fire rate quick enough for its mana cost that its single target damage lands above the gem staffs you would otherwise be carrying at this stage.

The weave has one odd benefit. Because the bolt swings sideways as it goes, it can slip through a half tile gap that a straight projectile would not fit through. Firing directly up or down cancels the weave and the bolt travels flat.