Medicine in Imperial Rome is an art of celebrated advances, an art of showmanship and bitter rivalry between practitioners all with their own entourages. There is one doctor above all others: Galenus. The writings of this second century Greco-Roman would be the epitome of medicine for one thousand years to come. The players enter this arena as doctors starting out by studying, treating patients, accumulating reputation and competing against each other in showy demonstrations. The goal of the game is to be the best young doctor, primus inter pares, by collecting the most favor in the eyes of Galenus over five rounds and thus becoming his friend and student. Galenus looms over everything the players do, and he will crush all who dare challenge him.

Galenus is a worker placement game where you place up to 6 action pawns and then decide when and how to resolve them. In this way some players can still be placing pawns while you are already resolving them. You can choose to cure patients, which will gain knowledge in one of four types of ailments, publish works based on that knowledge, show off your skills in the theater, acquire medicines to aid your work, rest to rejuvinate your own health, or adopt a new philosophy. At the end of the round you compete in medical contests via blind bidding that may give you more prestige. Whoever has the most points gained from these various tasks or first publishes 8 works wins the game.