Fingerclaws grasping at, scraping for sshhaaddeowss, the entity casts forth a multitude of hooked lines into one of the human's subtle bodies, the innumerable worms within his shadow sweeping sideways, waves wriggling towards a single point, threads swirling, whirling, wrapping together, coalescing into a massive coiled serpent, so large that the only parts of its darkness could be seen at one time within the man's shadow, arched, broad, curving lines of black within the gray: realizing, too late, that this is the wrong host, after all.
The head, short and rectangular, a big box shape mounted on a stringy neck flickering, wavering between varying degrees of thickness and thinness.
Too used to beings of more mundane, of less magical worlds, this necromancer's undead body is naturally building up an immunity far faster than it would have originally guessed.
But hunger and thirst, persistance and need, want and will...all of these thing leading to the entity to dig deeper, to try harder, with the memories of past experiences echoing in its mind, telling it that this is all it needs to do -- merely this and nothing more.
Yet a magical energy continues to prick at its threads, to pull it off, push it away; the cubical head thrashed on a neck made crooked with rapid, violent movements.
Feeling its grip loosening, its touch waning, a silent screech is sent from the shadows, sound waves imperceivable but nonetheless piercing to the ears.
The darkness fading, the entity coming to the inevitable conclusion, facing the realization that this time it is wrong, and closing in on the decision that it shall have to leave before any damage is done from being forced out, even at the cost of discovery.
Senses spanning surroundings, fanning out in the general area, but finding nothing of important interest to its own needs.
It shall have to search elsewhere for a suitable host -- supposedly in yet another waiting game.
So thinking, the human's shadow would appear to bulge outwards, as the shadowy entity bloats its body and pushes itself up against the borders, forcing its way out of the walls and into the air in a burst of liquid darkness, a dense fountain of black rushing upwards, skywards, away from both the necromancer and the rest of the grounded crowd.
A minute would be taken for the entirety of it to exit the man's shadows, to empty itself into the air; the fluid threads rolling together into a knotted spherical mass, just as a sleeping snake might.
The tangles in constant motion, only when all of it is in the air would the black phantasm raise its rectangular prism head, the only thing neither smooth in shape, nor entirely black in color; similar to a black transistor battery, its two snap connectors marked with silver stripes surrounding whorling white whirlpools.
The serpentine shadow would, for a brief moment, orient its polarized snaps towards the group below, before, in one smooth, swift movement, thrust its body upwards, out of its tangles and into a slick, slippery string slithering skywards, a mile or more of electrical cable stretching itself away towards sliding into an unreachable, interdimensional space, the entrance located within the reaches of its very own self.
Hopefully the sudden surprise appearance would be enough to shock and startle most present, particularly those few capable of seeing it and, even rarer, those who might be able to seal it away, into a stilled silence...enough ignorance and time for fulfilled flight.