Necron's Blade

 is a Dungeon Sword crafted with 24 Wither Catalysts and a Necron's Handle.

is used in 4 recipes as it is the unrefined version and can be refined into 4 other swords.

Essence Crafting
This sword has 4 refined versions called Hyperion, Astraea, Scylla and Valkyrie.

Each refined version is crafted using their respective precursor relic dropped from Giants that spawn in the Catacombs Floor 7 blood room. Each of the refined versions also specialize in different classes, for example Astraea is a tank sword that gives more while Valkyrie is better used for damage with its higher,  and.

Furthermore, the refined swords keep the  to Withers ability while adding a new ability that grants the sword   and  class specific stat per catacombs level to the sword.

Necron's Blade Scrolls
Necron's Blade Scrolls are items that can be applied onto a Necron's Blade to give it abilities on right click. The abilities are stackable and can be combined into a larger ability, Wither Impact. Instead of displaying separately it displays as a single ability with the names combined. There are 3 scrolls: Implosion, Wither Shield, and Shadow Warp.

Trivia

 * The 4 Refined swords all have Norse or Greek names from mythology. If bought from Post-Boss chests the cost is 56M