"The Soul Tether"
An ancient Elvin creation that was made to bind a dead gods soul to the material plane. However the tether failed and most of it was lost as the dead god's soul vanished. The remaining piece was taken by an ancient Bladesinger who crafted into a whip.
1d4+1 magic whip
While bladesinging you can use a bonus action to activate one of two abilities that can be applied to the next hit in that round:
+1d6 Necrotic damage to the targets maximum HP (does not affect Constructs or Undead).
+1d6 Radiant damage, the target must make a dexterity saving though (DC= 8+your Dex mod) or become blind until the end of the round.
Proficiency with a Whip allows you to add your proficiency bonus to the attack roll for any attack you make with it.
This weapon has the following mastery property. To use this property, you must have a feature that lets you use it.
Slow. If you hit a creature with this weapon and deal damage to it, you can reduce its Speed by 10 feet until the start of your next turn. If the creature is hit more than once by weapons that have this property, the Speed reduction doesn’t exceed 10 feet.
Notes: Damage: Necrotic, Damage: Radiant, Blinded, Damage, Combat, Finesse, Reach, Slow