Question: Helena Dragaš was the empress consort of the last reigning emperor of what empire?

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Helena Dragaš: Helena Dragaš (Serbian: Јелена Драгаш, "Jelena Dragaš" , Greek: , "Elenē Dragasē"; c. 1372 – 23 March 1450) was the empress consort of Byzantine emperor Manuel II Palaiologos and mother of the last two emperors, John VIII Palaiologos and Constantine XI Palaiologos.  Later in life she became a nun.  She is venerated as a saint by the Eastern Orthodox Church under her monastic name, as Saint (Ὑπομονὴ ), translated in English as "Saint Patience".

Fujiwara no Kinshi (Go-Shirakawa): Fujiwara no Kinshi (1134–1209) was an Empress consort of Japan.  She was the consort of Emperor Go-Shirakawa of Japan.  She was born as the daughter of Tokudaiji Kinyoshi.  She entered the Imperial Court and became a lady-in-waiting in 1155.  She was made Empress consort of Emperor Go-Shirakawa in 1156.  Emperor Go-Shirakawa abdicated 2 years later.  She was made Empress Dowager in 1172 and died at the age of 76 in 1209.

Empress Wang (Gaozong): Empress Wang (王玉燕) (died approximately 655 AD.)  was an empress of the Chinese dynasty Tang Dynasty.  She was the first wife and empress of Emperor Gaozong and became empress shortly after he became emperor in 649.  She, however, did not bear any sons for him and was not favored.  Therefore, in apprehension that one of his concubines, Consort Xiao, who was both favored and had a son, might seek to displace her, she recommended a former concubine of Emperor Gaozong's father Emperor Taizong, Consort Wu (later known as Wu Zetian), to be Emperor Gaozong's concubine as well, hoping to divert favor from Consort Xiao.  Soon, however, Consort Wu became dominant in the palace and overwhelmed both Empress Wang and Consort Xiao, eventually accusing them of using witchcraft against Emperor Gaozong.  Emperor Gaozong reduced both Empress Wang and Consort Xiao to commoner rank and put them under arrest in 655, replacing Empress Wang with Consort Wu.  Soon, Empress Wang and Consort Xiao were executed on the new Empress Wu's orders.

Emperor: An emperor (through Old French "empereor" from Latin imperator) is a monarch, usually the sovereign ruler of an empire or another type of imperial realm.  Empress, the female equivalent, may indicate an emperor's wife ("empress consort"), mother ("empress dowager"), or a woman who rules in her own right ("empress regnant").  Emperors are generally recognized to be of a higher honour and rank than kings.  In Europe the title of Emperor has been used since the Middle Ages, considered in those times equal or almost equal in dignity to that of Pope, due to the latter's position as visible head of the Church and spiritual leader of the Catholic part of Western Europe.  The Emperor of Japan is the only currently reigning monarch whose title is translated into English as "Emperor".

Zenonis: Aelia Zenonis (died 476/477) was the Empress consort of Basiliscus of the Byzantine Empire, brother of Verina.  Her sister-in-law was Empress consort to Leo I and mother to Ariadne.  Her niece Ariadne was Empress consort to Zeno and mother of Leo II.  Her ancestry is unknown.

Constantine XI Palaiologos: Constantine XI Dragases Palaiologos, Latinized as Palaeologus (Greek: Κωνσταντῖνος ΙΑ' Δραγάσης Παλαιολόγος , "Kōnstantinos XI Dragasēs Palaiologos", Serbian: Константин XI Драгаш Палеолог, "Konstantin XI Dragaš Paleolog" ; 8 February 1405 – 29 May 1453) was the last reigning Byzantine Emperor, reigning as a member of the Palaiologos dynasty from 1449 to his death in battle at the fall of Constantinople.  Following his death, he became a legendary figure in Greek folklore as the "Marble Emperor" who would awaken and recover the Empire and Constantinople from the Ottomans.  His death marked the end of the Roman Empire, which had continued in the East for 977 years after the fall of the Western Roman Empire.

Emperor Ping of Han: Emperor Ping (9 BC – February 3, AD 6) was an emperor of the Chinese Han Dynasty from 1 BC to AD 5.  After Emperor Ai died childless, the throne was passed to his cousin Emperor Ping—then a child of nine years old.  Wang Mang was appointed regent by the Grand Empress Dowager Wang.  Dissatisfied with his father's dictatorial regency, in AD 3, Wang's son Wang Yu (王宇) conspired with Emperor Ping's maternal uncles of the Wei clan against Wang, but after they were discovered, Wang had not only Wang Yu and the Weis (except Consort Wei) put to death, but also used this opportunity to accuse many actual or potential political enemies as being part of the conspiracy and to execute or exile them.  From here onwards, the Han Dynasty existed only in name.  Furthermore, Wang Mang also designated his daughter as the empress consort to Emperor Ping to codify his legitimacy to power.  Emperor Ping was allegedly poisoned by Wang Mang after reigning less than six years, because Wang was concerned that he would avenge his uncles, and his successor, the toddler Emperor Ruzi, would be chosen by none other than Wang Mang himself.

Empress Ma (Jianwen): Empress Ma (1378–1402), formally Empress Xiaominrang (孝愍讓皇后), was the Empress Consort to Jianwen Emperor and the second Empress Consort of China's Ming Dynasty.

Empress Lü Zhi: Lü Zhi (241–180 BC), courtesy name Exu (), commonly known as Empress Lü () and Empress Dowager Lü (), or formally Empress Gao of Han (), was the empress consort of Emperor Gaozu, the founder and first ruler of the Han Dynasty.  They had two known children, Liu Ying (later Emperor Hui of Han) and Princess Yuan of Lu.  Lü Zhi was the first woman to assume the title Empress of China.  After Emperor Gaozu's death, she was honoured as Empress Dowager and later as Grand Empress Dowager (太皇太后) during the short reigns of Emperor Hui and his successors Liu Gong (Emperor Qianshao) and Liu Hong (Emperor Houshao).

Maria of Trebizond: Maria Megale Komnene (Greek: Μαρία Μεγάλη Κομνηνή ), known as Maria of Trebizond (Greek: Μαρία της Τραπεζούντας ), (died 17 December 1439) was a Byzantine Empress consort by marriage to the Byzantine emperor John VIII Palaiologos (r. 1425–1448).  She was the last empress consort of the Byzantine Empire.

Supporting paragraphs: Helena Dragaš Constantine XI Palaiologos
Answer: Byzantine