Seedler

Each swing lobs a nut that drops in an arc and then bursts into a scatter of thorns that go looking for targets on their own. All of those thorns can land on the same enemy if it is the only thing nearby, so the number on the tooltip badly understates what the sword actually does. Judge it by what happens when the nut detonates, not by the swing itself.

The nut has to travel and burst before any of that happens. Fighting in a corridor throws most of it away, since the nut clips a wall early and the thorns have nowhere to spread. Wide caverns, the surface and event arenas are where it pulls ahead of swords with better raw numbers.

The seeking thorns treat each segment of a worm boss as its own target, so a single burst inside the Destroyer spreads across the body instead of hammering one point. Invasions and eclipses get the same benefit for the same reason. This is the weapon to reach for whenever the screen is full.

It is a component of the endgame sword, so keep one in a chest even after you have moved on. It is also the direct successor to the early jungle blade, which is a rare case of an early weapon getting a proper upgrade rather than being replaced by something unrelated.