Short answers, pulled from the story.
Zeno was the Eastern Roman emperor who ruled from 474 to 475 and again from 476 to 491. Born Tarasis in Isauria, Cilicia, he was an Isaurian general who became emperor through his marriage to Ariadne, daughter of Emperor Leo I. His reign spanned the fall of the Western Roman Empire and lasted seventeen years and two months.
Zeno was overthrown in January 475 by a conspiracy led by the dowager Empress Verina, who wanted to replace him with her lover Patricius, and her brother Basiliscus. The generals Illus and Trocundes, along with the Ostrogothic general Theodoric Strabo, joined the plot. Zeno fled Constantinople for his native Isauria, taking Ariadne, his mother, and the imperial treasury.
The Henotikon, meaning "Act of Union", was a religious edict issued by Zeno in 482 to mediate between Chalcedonian and Miaphysite Christians over the nature of Christ. Developed with the Patriarch of Constantinople Acacius, it affirmed the Nicene-Constantinopolitan Creed, condemned both Eutyches and Nestorius, and described Christ as "one and not two" without explicitly endorsing or rejecting Chalcedon. Pope Felix III rejected it and excommunicated Acacius in 484, beginning the Acacian schism that lasted until 519.
In 476, the Germanic chieftain Odoacer deposed the last western emperor, Romulus Augustulus, and sent the imperial regalia to Constantinople. Odoacer explicitly acknowledged Zeno's suzerainty over the West, making Zeno the theoretical sole ruler of a reunified empire. Zeno in turn recognized Odoacer's de facto control of Italy, formalizing an arrangement that acknowledged the Western Empire was gone.
Zeno attempted to keep the two Ostrogothic leaders, Theoderic the Amal and Theodoric Strabo, fighting each other rather than threatening Constantinople. After Strabo died in an accident in 480-481, Zeno appointed Theoderic the Amal consul in 484, the first non-citizen barbarian to hold that distinction. He ultimately resolved the Gothic threat by sending Theoderic to Italy in 487 to defeat Odoacer and establish the Ostrogothic Kingdom there.
In 480, Emperor Zeno was playing tabula, a game nearly identical to modern backgammon, and encountered a position so disastrously unlucky that he wrote an epigram about it. He held seven checkers in one stack, three stacks of two, and two exposed lone pieces, then rolled 2, 5, and 6 on three dice. The rules required him to use all three results, but every possible move would break his two-checker stacks and expose them to capture. The poet Agathias preserved the epigram roughly fifty years later, and some historians call it the first recorded bad beat story in human history.