The Black Sword's Bargain
Since Ehlonna crossed from Faerun, two years ago and made her pact with the Black Sword, she knew that she would be called upon to perform a task. She just didn’t know if she would be able to pay the price.
With the acquisition of a Sun Blade, the Black Sword has a new task for Ehlonna – corrupting the Sun Blade and making it an instrument of the Shadowfell. With the corruption of the Sun Blade, a new Night Blade will be forged.
Night Blade – blade of Shadowfell energies – proficiency in long sword or short sword required, versatile, requires attunement, 1d8 magic slashing damage + 1d8 necrotic to living creatures
The blade dims light within 15’ – bright becomes dim, dim becomes darkness – this property can be suppressed by the wielder.
That weapon is very rare levels of niceness, but since it should take a number of quests to complete and at that point it would be my end all kind of blade.
Thinking about it last night – it could be sorta Frostbrandish? 1d8+1d6 necrotic – the blade can extinguish or suppress a light spell.