Terraprisma

Every point of damage you deal to the Empress of Light has to land while it is daytime, and in daylight she is enraged and kills nearly anything she touches in a single hit. There is no partial credit and no reduced chance for a mixed attempt: chip her once at night and that run is spent. Get it right and the drop is guaranteed, which is the one mercy in the whole thing. Most people who own one earned it over a long series of ninety second attempts, and the fight is usually won on movement gear rather than on damage.

The swords hold a fixed wing formation behind you and dive with tracking no other minion matches. They pick up targets fast, they do not wander off, and they stay relevant through everything left in the game. The Stardust Dragon Staff posts bigger raw numbers but comes apart against the Lunar Events, Duke Fishron and the Empress herself, where this barely notices the difference. Running both together covers each one's weak spots. The precise movement and fixed idle position put it in the same family as the Blade Staff and Sanguine Staff, except at the top of the progression instead of the middle of it.

They will not pass through terrain to reach a fresh target. Once they have connected with something in the open, though, they stop caring about walls entirely and will chase follow-up targets straight through solid ground before returning to you. Fighting with your back against a wall works in your favor for that reason rather than against you.

Fabled is the default answer and stops being correct once your summon damage bonuses climb high enough, at which point Ruthless pulls ahead. A late summoner running a full whip rotation is likely already past that line, so it is worth checking the total rather than reforging for Fabled on reflex.

The sprite is a sword and the item is a summon weapon, which catches people out. The tooltip's talk of enchanted swords is flavor and has nothing to do with the Enchanted Sword item or the enemy of that name. The blade is bright enough that basic, bright and gradient dyes barely register on it, though compound and most strange dyes do come through, and the rainbow trail keeps its own colors no matter what you apply. The formation is actually a helix, which only becomes visible with more minions than the game normally allows. Like the Last Prism, it hides alternate color themes that unlock on specific character names.