This form is used by the sages of the Negative Plane who have been remade by the power of the Nether, the substance that fills the Negative Plane. Voidsages, often regarded as "Dark Weavers," techniques and abilities are drawn from the power of their negative emotions. 

In this state, you can unleash the dark cosmic power, Nether. You can undergo this transformation a number of times equal to your proficiency bonus per long rest. As a bonus action for the next minute, you gain the following. 

• You gain a +1 to spell attacks, and your spell DC is increased by 1
• You deal an additional 1d10 necrotic damage on spell attacks. 
• You become immune to necrotic damage.

While you are transformed, you can call on the powers nether to aid you in combat.