You’ve been warned:
Cortana is ugly in this game.
Thats not a spoiler and is clearly an opinionated opinion.
Cortana is ugly in this game.Besides being an opinionated observation, there are three reason why she is visually different canonically, developer-wise and community relations.
Canonically
Smart-AI can change their avatar at will to serve their purpose or liking, some don’t humanize themselves (ie Black-Box), others do (Cortana, Serina)…
Developer-Wise
Developing Halo 5: Guardians on the Xbox One would have different hardware which could reap different benefits from the Xbox 360. Cortana’s new iteration being designed differently is also perhaps due to the animating and difficultly with getting the original motion-actor that was in Halo 4, some reasons could be due to availability or cost, so another actor was put in place.
Community Relations
In the community, Cortana has always been seen as a protagonist, second to none other than John-117. She has always had an iconic look about her in each Halo iteration however as her role has clearly been defined as antagonistic, 343 Industries wants fans to see her in a familiar yet different light, resembling to her former self, personality and outlook on Humanity yet having deeper meaning, views and purpose, in this case the survival of her kin, the AI. She is also suppose to be a emotionless tyrant without remorse so her face is deemed emotionless and mature, rather than fair and innocent, perhaps this is due to her bonding with the domain and also gaining surmountable records of the past about the Flood, Forerunners and Pre-historic Humans.