Voidling

Writhing black tendrils stretch from this indistinct orb of pure shadow. The faintest flicker of something green, like an eye, appears for a moment in the center of the globe and then fades to black again.
Called from Darkness. Voidlings are creatures of the darkest void, the cold space between the stars, drawn to mortal realms by practitioners of foul and corrupting magic known to break the minds of those who wield it. They frequently are summoned servants to void dragons, and they have been seen as wardens of the temples on the Plateau of Leng.
Light Eaters. They are said to devour life and knowledge and light itself as sustenance; the places they inhabit are known for their dank chill and their obscurity. Voidlings are summoned by those hungry for power at any cost, and—despite their dark reputation—they serve very well for years or even decades, until one day they turn on their summoners. If they succeed in slaying their summoner, they grow in strength and return to the void. Exactly what voidlings seek when they have not been summoned—and what triggers their betrayals—is a mystery.
Cold Tendrils. Creatures of utter darkness, they can barely be said to have a shape; they consist largely of lashing tendrils of solid shadow. The tendrils meet at a central point and form a rough sphere in which something like an eye appears intermittently.
Though their tentacles stretch 10 feet long, the core of a voiding is no more than 4 feet across, and it weighs nothing, darting through either air or void with impressive speed.