Multi-plane Existence: The Void Elemental can exist on both the Astral Plane and one other plane of its choice.

Formed of Void: The Void Elemental is immune to cold damage

Spacial Awareness: The Void Elemental has advantage on perception and investigation checks and saves. 

Ancient Being:  Void Elementals know the history of almost any creature, construct, or other living creature that has existed in the last three billion years and will automatically succeed on any history check against a creature, construct, etc.

Superior Intelligence:  Void Elementals have advantage on Intelligence checks and saves.

Multiattack. The Void Elemental makes four claw attacks and two bite attacks.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 67 (12d8 + 35) slashing damage.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 43 (8d8 + 20) piercing damage. Enemy must make a DC 16 Con save or be poisoned

Legendary Resistance (3/Day). If the Legendary Resistance (3/Day). If the Void Elemental fails a saving throw, it can choose to succeed instead.

Innate Spellcasting. The Void Elemental’s innate spellcasting ability is Intelligence (spell save DC 20). It can innately cast the following spells, requiring no material components:

At Will:     Ray of Sickness, Blight, Shadow of Moil, Cause Fear

3/Day:     Circle of Death, Eyebite, Harm, Finger Of Death

1/Day:    Abi-Dalzim's Horrid Wilting