Short answers, pulled from the story.
Baybars was the fourth Mamluk sultan of Egypt and Syria, ruling from 1260 to 1277. He is significant for leading the Mamluk vanguard at the Battle of Ain Jalut in 1260, the first substantial defeat of the Mongols, and for his campaigns that dismantled most of the Crusader states in the Levant, including the capture and destruction of Antioch in 1268.
Baybars rose from slavery to become a military commander under Sultan Qutuz. After the Mamluk victory at the Battle of Ain Jalut in 1260, Qutuz was assassinated during a hunting expedition; reports from the period hold that Baybars was involved, motivated by Qutuz's refusal to grant him the governorship of Aleppo. Baybars then assumed the sultanate.
Baybars captured Antioch on the 18th of May 1268, after laying siege to the city. Despite promising to spare the inhabitants, he had the city razed and its population killed or enslaved. Contemporary accounts called it the single greatest massacre of the entire crusading era, ending the Principality of Antioch.
Baybars was of Turkic Kipchak origin, born in the steppe region north of the Black Sea between approximately 1223 and 1228. He was taken captive during the Mongol invasion of Bulgaria around 1242, after witnessing his parents' massacre, and was sold into slavery at the market in Sivas in the Sultanate of Rum. He entered Egyptian service after being confiscated by Sultan As-Salih Ayyub in 1247.
Baybars set out from Cairo in early 1276 and defeated Nubian forces in three battles, at Gebel Adda, Meinarti, and Dongola. King David of Makuria fled south and was handed over to Baybars by the king of al-Abwab, after which David was executed. Makuria was reduced to a vassal kingdom, required to pay jizya tribute, with its king chosen personally by Baybars.
Baybars died in Damascus on the 30th of June 1277, at age fifty-three. The most widely reported account holds that he accidentally drank poisoned kumis intended for someone else, though other accounts attribute his death to a battle wound or illness. He was buried in the Az-Zahiriyah Library in Damascus.