Mental Fortress. The Voidweaver is immune to all mentally altering effects such as charmed, frightened, dominated, or any other effects that affect the mind.

Fire Weapon(Melee). Voidweaver Gauntlet: +8 to hit, reach 5 ft., 1 target. Hit: 7 (2d4 + 2) piercing damage.
The Voidweaver aims its gauntlet at the target and fires a beam of energy toward it.

Fire Weapon(Ranged). Voidweaver Gauntlet: +6 to hit, range 45/90 ft., 1 target. Hit: 7 (2d4 + 2) piercing damage.
The Voidweaver aims its gauntlet at the target and fires a beam of energy toward it.

Astral Conduit (Used as an Action). The Voidweaver opens a mysterious rift at its feet and pulls a strange energy out of it. After doing this the Voidweaver falls to its knees and is surrounded by an impenetrable translucent dome. While within this shield, the Voidweaver becomes immune to all damage and cannot perform actions, bonus actions, or movement. This ability can be used once per minute.
(When the Voidweaver performs this action, roll 1 d8. The summon will be one of these 8 results: 1. "The Ravager - Butcher of Wrath" 2. "The Devourer - Jaws of Gluttony" 3. "The Jaundiced - Drudge of Envy" 4. "The Hoarder - Plunderer of Greed" 5. "The Slumberer - Wallow of Sloth" 6. "The Imperious - Sovereign of Pride" 7. "The Temptress - Charmer of Lust" 8. "The Silenced - Shadow of Despair" Each of these entities has its own stats. Further descriptions of each of these summons are given in their monster descriptions.)
-The Void answers my call.

Sustain (No Action Cost). When the Voidweaver takes enough damage to fall to or below 0 hit points, it is instead reduced to 1 hit point. A purple mist spills from its wounds and forms a translucent purple dome around the Voidweaver. The Voidweaver remains within the shield until its turn in initiative when the shield disappears and the Voidweaver can perform actions. While within the shield, the Voidweaver is immune to all damage. When sustain ends, the Voidweaver remains immune to damage if it would use Astral Conduit during its turn and does not perform any other actions, bonus actions, or movement.
-Not so fast!