The game centres around the historical 16th-century physician and astrologer Simon Forman and the characters he encounters, who demand diagnoses, treatments, and sometimes to be read fortunes written in the stars.

The player controls Simon Forman (Dave Jones), a real-life astrologer, occultist, and herbalist active in London during the reigns of Elizabeth I and James I of England.

After examining the skies for hints about patients' personal lives, the player can suggest a treatment or course of action for them.

The game was developed by Nyamyam after creative director Jennifer Schneidereit saw Lauren Kassell present her research on Simon Forman's casebooks at the University of Cambridge.

In 2023 Astrologaster was featured in the British Library Digital Storytelling Exhibit,[19] during which a Q&A was held with Schneidereit and Kassell alongside performances of songs from the game's soundtrack by a live vocal quartet.