The Emperor, a two-performer meditation on the man-made mythos of power, is part Brechtian commentary, part clown show, part investigation of the last days of a real regime — that of the Ethiopian monarch Haile Selassie, whose four-decade reign ended when he was deposed in 1974 — and part playful, piercing allegory. It’s a concentrated, compelling piece of theater with a light touch, recently adapted by Colin Teevan from a 1978 book by the Polish journalist Ryszard Kapuściński.