Newt's obscurus

The Obscurus

An Obscurus was the manifestation of the repressed energy of a magical child (known as an Obscurial). Described as a "dark" and "parasitic" force, an Obscurus was created when the child in question was forced to repress their talent through physical or psychological abuse. This energy could manifest itself as a separate entity that can erupt in violent, destructive fury.
When an Obscurial lost control, the Obscurus force was released, often focused on the cause of the Obscurial's torment, but also causing destruction in its wake.

The Obscurus could be largely invisible or appear as a flying, incorporeal, and amorphous entity with the appearance of a black, fluid-like cloud, or a violent torrent of darkness, sometimes with a reddish core. Some described it as a "dark wind" or "dark mass" with "shining white eyes". Its appearance could be oleaginous, or "rich in, covered with, or producing oil, or oily or greasy". There have also been instances when a face briefly emerges from the shadowy entity, or a white glowing image of the host appears inside of it.

The size and might of an Obscurus depended on the innate power of its host; the more powerful an Obscurial, the more powerful their Obscurus. When an Obscurial reached their emotional and mental breaking point, they could lose control completely and physically transform into an Obscurus. Its size and mass at specific times may also have be connected to the level of negative emotions that triggered it at that instance, as well as the current mental state of its host.

In this state, they are enormously destructive to their surroundings, to the point of causing objects to levitate or break without physically being in contact with them. This notably causes damage to structures and objects near the host. However, they could be calmed down by someone they trust, which caused them to revert to their corporeal state, though being emotionally conflicted could cause the Obscurial to transform back and forth.