It wasn't known what role Harington would play - in fact, it was thought that it could be as small a part as Marshawn Lynch’s Black Ops III cameo. But now we know that Harington will be the villain of the piece.
Harington is to put a face to the enemy, the Settlement Defence Front, according to narrative director Taylor Kurosaki.
"It meant a lot to us to develop the role into everything it could be. We're excited about the performance Kit delivered and can't wait to get it out to the public," Infinity Ward studio head Dave Stohl said in a statement accompanying the announcement.
Harington isn't the only big name attached to the project. Guy Ritchie was brought in to assist on production while Harington was filming.
We may see the result of their work at E3. Call of Duty: Infinite Warfare will be released on November 4.