Indigo Keen is a mermaid princess. She is known as a nice and very playful girl. As the ruler of the Deep Sea Kingdom and a user of shadow manipulation, she never knew about her past after her kingdom was destroyed by Black Diamond. She is a warm-hearted person who uses the Shadow Cane to manipulate shadows and can transform into a shadowy blob. She is also a hero that know one knows.

Indigo Keen has four distinct forms, each with unique clothing and physical traits:

Human Form: She wears a light indigo long-sleeved hoodie featuring a crescent moon on the chest, paired with a black skirt, indigo socks, and dark brown shoes. She also wears a yellow ring with a moon symbol.

Mermaid Form: Her mermaid attire consists of an indigo tank top with a navy-blue crescent moon and light purple straps. She wears a light purplish-blue tiara, and her indigo tail—which has fins shaped like a crescent moon—is wrapped with a golden band near the fins.

Magical Girl Form ("Lunatic Indigo"): In this form, she wears an indigo top hat and an indigo dress adorned with a rainbow crescent moon. Her outfit includes indigo gloves and tall indigo boots with thick rainbow outlines.

Shadow Form: A fourth form where she becomes a shadowy blob of darkness, allowing her to slither quickly or escape dangerous situations.

Powers: Utilizing the Shadow Cane, she can manipulate shadows and use the "Shadow Pin" to freeze her enemies.

Personality: Very Playful, Warm-hearted hero.