Antagonist (AKA Mr Ant, Mr A or similar)
In his natural form a blob of amorphous ink that drips through the cracks in stories. However when interacting with protagonists he always assumes the form of a smart monochrome male figure appropriate to the setting.
Antagonist was created recently as a result of the unwriting of the book. Just as the Book became aware of its need for mortals to stop the unwriting, so too did it unconsciously create something to rally against its chosen ones because stories always have two sides. Antagonist is a combination of elements from different stories that have already collapsed into chaos.
A polite exterior hides a curmudgeon with a purpose. Antagonist is not yet a creature capable of true creation, so he revels in unravelling the efforts of others. A true cynic who sees all the protagonists around him as hollow shells of tropes and clichés.
When dealing with others he tries to expose their flaws and distract them from their own story. Challenging them to be worthy of having a story told about them, those who fail only add depth to his existence.
Inherently non-violent, Antagonist is well aware that protagonists always win physical confrontations.
However he has soft spots. Being a 2-dimensional figure he is impressed by depth in others. If he finds somebody genuinely conflicted he nurtures it, tries to sway them to join him and may assist them by providing information about the book or coincidental changes in the story.
Antagonist knows that his world is collapsing and he instinctively feels a call to action. He wants to survive the end of his paper world and whether by creating a new Book, restoring the old or escaping to the unknown that exists outside the books pages. He will survive.
He is bound to the book and can not leave it, yet. Made from ink on paper he can inhabit any passing Figment and shape it to his purposes, so whilst he can be killed easily, it is usually a temporary setback as the ink flows through to another page. The gifts of Lady Ink, Mudd and the Book however can easily destroy him.
He is aware of the narrative around him at all times, making him dangerously genre savvy. He is however limited in what he can do. He can't make major changes to a story. He can try to suggest, nudge and direct others who have a genuine creative spark, or he can manipulate elements of a story that are already established or fill in small details that have yet to be defined, but he is a character not an author, a fact that he is frustratingly aware of.
Who they were chosen by:
Nobody chose him, he was a mistake or a part of the design, but ultimately nobody supports the Antagonist except themselves.
Description of their gift if any:
None and he's bitter about that.