Aiden is an Entity that has been linked to Jodie Holmes since birth. They are connected by an ethereal tether, that can be seen when switching to Aiden's view. This tether acts as a spiritual link between Jodie and Aiden that keeps Aiden bound to Jodie. Though he can go farther away from Jodie in some situations, the separation causes Jodie excessive amounts of pain and lasting disorientation. Throughout the game, Aiden shows that he is capable of human emotion through his interactions with Jodie and his own frustration at the restraining tether.
Jodie is the only one capable of listening to or communicating with Aiden. Cole Freeman and Ryan can also communicate with Aiden when Jodie is being sedated by the CIA. However, she does not instruct Aiden. Aiden is not under her control. Although he is tethered to her, he is in full control of his actions. She can request his help, but not demand it. He tries to stop her when he disagrees with her, not by directly hurting her, but by making obstacles for her. We do not know what Aiden's main goal in the game is, although he appears to think of Jodie as his charge.
Jodie and Aiden seem to age in sync, for as Jodie grows older, Aiden grows stronger, and their bond grows greater. The powers displayed by Aiden include a powerful psychokinetic thrust that can move physical objects and damage spiritual entities, basic possession skills that allow him to take over the minds of nearby humans, a Vaderian "force choke" that he uses to strangle various hostiles, psychic abilities that allow him to direct mnemonic imprints from certain spots to Jodie for her to experience, and the ability to "read" the souls of recently dead human beings, the technical term being mediumship. He can also heal Jodie and the people who Jodie directs him to heal.