Demon Scythe

A cast sickle hangs almost motionless for a moment before it starts building speed, and it keeps accelerating until it is moving very fast. It can connect with the same enemy several times before it gives out. That shape means the weapon is at its best point blank, where the target sits inside the sickle for the whole slow phase and eats every hit. Fired across a room at something distant, most of that damage never happens.

Piercing and persistence make it disproportionately good against anything built from segments or spawned in bulk. The Eater of Worlds folds to it. During the Wall of Flesh it clears The Hungry and the Leeches while still landing on the boss behind them. Demons spawn in the Underworld for the entire game, so this is one of the few genuinely strong weapons you can go and fetch at any point, assuming you can survive down there long enough to farm it.

Most magic weapons want a Mana Potion. This one wants regeneration potions instead. Because the sickles keep working after they leave your hands, you can afford to run dry and let mana come back on its own, whereas chugging restores stacks Mana Sickness and cuts the damage of every cast that follows. It is also one of the cheapest weapons in the game to reforge, so getting Mythical on it is not a project.

The sprite is a recolored Water Bolt. Roll the Demonic modifier on it and you end up with the Demonic Demon Scythe.