Orb of deteriorating mojo

This item can be used as a +1 casting focus that can replace any spell damage with necrotic damage.
All allies within 20ft gain a +1d4 necrotic damage to all damage rolls.
As a bonus action all allies within 20ft deal an additional 1d4 necrotic damage to all damage rolls till the start of your next turn.

History

From Enderdragon Encounter

Rarity

very rare wonderous item ( requires attunement by a caster)