First referenced:
The Portal in the Forest (Part 4)
The Regret Demon is a mostly unknown entity that presents trade options that invariably lead to remorse and regret. The Regret Demon was first encountered by Cristina Thompson after it hijacked the primary forest portal to discuss a truce.
As a form of communication interface, the Regret Demon used a human woman, described as middle-aged and wearing wire-rimmed glasses, as a puppet. It is unconfirmed whether the puppet woman was fully human, however she appeared to resist being recaptured by the neural tissue, and through subtle abnormalities in responses to queries communicated valuable information to Cristina Thompson without the Regret Demon extracting payment in response.
Traits:
Apparently a large organism, capable of redirecting interdimensional portals and generating tangible illusions or matter. Comprised of neural tissue in a similar fashion to the Dreamer On High entity, the Regret Demon has at least one (and likely more) enslaved humans under direct mental control.
Displays hostility and fear towards the Soul Reader (Book), likely due to its ability to read information forcibly from souls without the need of providing payment.