Short answers, pulled from the story.
Nader Shah was the founder of the Afsharid dynasty of Iran, ruling as Shah from 1736 until his assassination on the 20th of June 1747. Born Nadr Qoli, he rose from nomadic poverty in Khorasan to become the most powerful ruler in the region, commanding an empire that stretched across parts of modern-day Afghanistan, India, Iraq, Turkey, and the Caucasus.
Nader Shah defeated a Mughal army of roughly 300,000 men in under three hours at the Battle of Karnal on the 13th of February 1739, despite being outnumbered five to one. After entering Delhi and facing a retaliatory attack that killed 900 of his soldiers, he ordered the city sacked on the 22nd of March 1739, resulting in the deaths of 20,000 to 30,000 people. He seized the Peacock Throne, the Koh-i-Noor and Darya-ye Noor diamonds, and treasures estimated at seven hundred million rupees, enough to suspend taxation in Iran for three years.
Nader Shah was assassinated at his camp at Quchan in June 1747 by a group of conspirators from within his own guard. After his plan to arrest the guard leaked, four conspirators entered his tent at night; Muhammad Quli Khan struck him with a sword first, and Salah Khan then severed his head. The eyewitness account was recorded by his physician Père Louis Bazin, based on testimony from Chuki, one of Nader's favorite concubines.
Nader Shah introduced a form of Shia Islam he called the Ja'fari school, named in honor of the sixth Shia imam Ja'far al-Sadiq, as an attempt to make Iranian religion more acceptable to Sunni Muslim powers including the Ottomans. He banned Shia practices offensive to Sunnis, such as cursing the first three caliphs, and sought to have Ja'farism recognized as a fifth school of Sunni Islam. The Ottomans refused to grant that recognition but did allow Iranian pilgrims to perform the hajj in Mecca.
Nader rose from a minor military role under Safavid claimant Tahmasp II, recapturing Mashhad in 1726, defeating the Afghan forces that had taken Isfahan, and restoring much of Iran's lost territory. When Tahmasp II signed a disadvantageous peace with the Ottomans in Nader's absence, Nader forced him to abdicate in 1732 in favor of the infant Abbas III and became regent. He convened a grand assembly on the Moghan plain in January 1736, secured a formal document of consent from nobles and clergy, and was crowned Shah of Iran on the 8th of March 1736.
Nader Shah's empire collapsed almost immediately after his assassination in June 1747, with nearly every provincial governor declaring independence. Ahmad Shah Durrani, whom Nader had summoned on the night of his death, proclaimed independence and founded what became modern Afghanistan. Erekle II, who had served under Nader in India and whom Nader made king of Kakheti in 1744, unified eastern Georgia as the Kingdom of Kartli-Kakheti. Iran fell into civil war until Karim Khan founded the Zand dynasty and became its ruler by 1760.