5Dropped by
the projectile is the weapon
The sword itself swings with a hitbox that reaches noticeably further than the blade you can see, wider than almost anything else at that point but shorter vertically. The reason to carry it is the crescent it throws. Those pass through walls, cut through several enemies before they stop, and fade after about a second, so each swing covers a band in front of you rather than a single point.
melee speed does almost nothing
The crescents come out on a fixed timer that melee speed bonuses do not touch. Stacking attack speed makes the blade wave around faster without producing any more projectiles, so the usual melee speed buffs and modifiers are worth less here than they look on paper.
what it is good at
Piercing plus wall penetration means you can sit behind arena blocks and keep dealing damage, which covers both crowd clearing and bosses that like to burrow or phase through terrain. Against a single large target you land the swing and the projectile together, so it holds up as a straight damage weapon as well. It drops from Betsy at the top tier of the Old One's Army, and like the rest of that loot it takes its name from a Dungeon Defenders 2 weapon.