Mabaran Ebony Rod

Arcane Focus: An arcane focus is a special item designed to channel the power of arcane spells. A sorcerer, warlock, or wizard can use such an item as a spellcasting focus.

An imbued wood focus is a rod, staff, or wand cut from a tree infused with extraplanar energy. If you're a spellcaster, you can use this item as a spellcasting focus. When you cast a damage-dealing spell using this item as your spellcasting focus, you gain a +1 bonus to one necrotic damage roll of the spell.