The rules of 20 questions (aka animal, vegetable or mineral) are that someone things of an object/person/plant and the rest ask questions about it. The person having thought of the object answers yes or no. Gradually the questioners narrow down things until they are able to guess.
So how about trying it in Ancient Greek? Perhaps to start with it would be a good idea to narrow it down to a person from Ancient Greek History or Literature (not necessarily Greek).