Short answers, pulled from the story.
Pescennius Niger was a Roman general and imperial legate of Syria who was proclaimed emperor by the eastern legions by the end of April 193. He claimed the throne in response to the murder of Pertinax and the auctioning of the imperial title to Didius Julianus, after Roman citizens publicly called for him to take power.
Severus outmaneuvered Niger militarily and politically. He entered Rome in early June 193 after Julianus was murdered, then marched east with sixteen Danubian legions against Niger's six. His generals defeated Niger's forces at Cyzicus in the fall of 193 and at Nicaea in December 193, before Severus' commander Publius Cornelius Anullinus decisively defeated Niger at Issus in May 194.
Niger was captured near Antioch in 194 while attempting to flee toward Parthia and was beheaded. His severed head was taken to Byzantium and later displayed in Rome.
The name literally means black Pescennius. Cassius Dio recorded that a priest of Jupiter reported a dream of a dark man breaking into the emperor's camp, interpreted as referring to Niger. The Historia Augusta notes that his father bore the cognomen Fuscus, meaning brown, and describes Niger as having a pale body with a dark-red face and a very black neck.
The Year of the Five Emperors refers to 193 AD, when five men held or claimed the Roman imperial title: Pertinax, Didius Julianus, Pescennius Niger, Clodius Albinus, and Septimius Severus. Niger was the eastern claimant, proclaimed emperor by his legions in Syria by the end of April 193 but defeated and killed by Severus in 194.
The Historia Augusta claims Severus had Niger's wife and children put to death and confiscated his estates. However, Roman scholar Geoffrey Turton argued that Severus refrained from such reprisals and that Niger's family was allowed to live in quiet retirement, since they were no longer useful as hostages after Niger's death.