Void Archon

Void Aura. Dim, violetish light spreads within a 20-foot-radius sphere centered around the archon. The light spreads around corners. When a creature moves into the aura's area for the first time on a turn or starts its turn there, that creature must succeed on a DC 20 Constitution saving throw or take 4d10 necrotic damage, and it suffers one level of exhaustion and emits a dim, violetish light in a 5-foot radius. This light makes it impossible for the creature to benefit from being invisible. The light and any levels of exhaustion caused by this aura go away when the creature leaves the aura. 

Living Shadow. While in dim light or darkness, the voidsent has resistance to damage that isn’t force, psychic, or radiant.

Shadow Stealth. While in dim light or darkness, the voidsent can take the Hide action as a bonus action.

Shackles of the Void. The archon's wings are locked in place as they create wholes in reality that anchor them in place. Therefore, the only way the Void Archon can move is by teleportation. However, because of these shackles, the Archon is immune to any effect that would move it or knock it prone.

Spellcasting. The [monster name] is a #-level spellcaster. Its spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). The Archon has following spells prepared:
At Will: Dimension Door, Elemental Bane, Magic Missile(5th Level), Misty Step,
8th level (1/day each): Finger of Death, Plane Shift (Back to the Void).

Reality Tear (Recharge 5-6). The Archon rips into the fabric of space, blasting creatures with a wave of raw void energy, at a point within 150ft that it can see. This tear creates a 30-foot cube centered on a point chosen. Each creature in that area must make a DC 20 Constitution saving throw. Constructs and undead aren’t affected. A creature takes 12d8 necrotic damage on a failed save, or half as much damage on a successful one. Nonmagical plants in the area that aren’t creatures, such as trees and shrubs, wither and die instantly.

Reality Shift. In response to taking damage, the Archon can use its reaction to cast Misty Step.