Necron's Blade

Necron's Blade is a sword crafted with 24 Wither Catalysts and a Necron's Handle.

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

Essence Crafting
This can be upgraded with Wither Essence. 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 VII blood room. Each of the refined versions also specialize in different classes, for example Astraea is a tank sword that gives more defense while Valkyrie is better used for damage with its higher damage, strength and ferocity.

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.

Trivia

 * The 4 Refined swords all have Norse or Greek names from mythology.