Question: Who conspired to kill David Rizzio, the lover of Mary, Queen of Scots?

Context paragraphs:
Casket letters: The Casket letters were eight letters and some sonnets said to have been written by Mary, Queen of Scots, to the Earl of Bothwell, between January and April 1567.  They were produced as evidence against Queen Mary by the Scottish lords who opposed her rule.  In particular, the text of the letters was taken to imply that Queen Mary colluded with Bothwell in the murder of her husband, Lord Darnley.  Mary's contemporary supporters, including Adam Blackwood dismissed them as complete forgeries or letters written by the Queen's servant Mary Beaton.  The authenticity of the letters, now known only by copies, continues to be debated.  Some historians argue that they were forgeries concocted in order to discredit Queen Mary, and ensure that Elizabeth I supported the kingship of the infant James VI of Scotland, rather than his mother.  The historian John Hungerford Pollen, in 1901, by comparing two genuine letters drafted by Mary, presented a subtle argument that the various surviving copies and translations of the casket letters could not be used as evidence of their original authorship by Mary.

Babington Plot: The Babington Plot was a plan in 1586 to assassinate Queen Elizabeth I, a Protestant, and put Mary, Queen of Scots, her Roman Catholic cousin, on the English throne.  It led to the Queen of Scots' execution, a direct result of a letter sent by Mary (who had been imprisoned for 19 years since 1568 in England at the behest of Elizabeth) in which she consented directly to the assassination of Elizabeth.

The Black Math Experiment: The Black Math Experiment is a band described as a unique blend of 1980s synthpop and new wave music with similarities to “The B-52's crossed with Berlin, The Dead Milkmen, and Talking Heads.”  Based in Houston, Texas in 2004, the band is known for their offbeat pop songs with irreverent or strange lyrics (for example, "Evil Wizard Jesus").  They are known for elaborate live shows that integrate multimedia such as televisions endlessly running odd videos, evangelical-like pamphlets and baptisms, Christmas presents, and a toilet paper cannon, all led by the inexhaustible energy of lead singer Jef With One F (Jef Rouner).  They received notoriety with their song, “You Cannot Kill David Arquette”.

Margaret Tudor: Margaret Tudor (28 November 1489 – 18 October 1541) was Queen of Scots from 1503 until 1513 by marriage to James IV of Scotland and then, after her husband died fighting the English, she became regent for their son James V of Scotland.  She was born at Westminster Palace as the oldest daughter of Henry VII of England and Elizabeth of York, and granddaughter of Margaret Beaufort, Edward IV of England and Queen Elizabeth Woodville.  Margaret Tudor had several pregnancies, but most of her children died young or were stillborn.  As queen dowager she married Archibald Douglas, 6th Earl of Angus.  Through her first and second marriages, respectively, Margaret was the grandmother of both Mary, Queen of Scots, and Mary's second husband, Lord Darnley.  Margaret's marriage to James IV foreshadowed the Union of the Crowns – their great-grandson, James VI and I, was the first to be monarch of both Scotland and England.

Mary Queen of Scots (2018 film): Mary Queen of Scots is an upcoming British-American historical drama film directed by Josie Rourke and written by Beau Willimon.  It is based on John Guy's biography "My Heart Is My Own: The Life of Mary Queen of Scots".  The film stars Saoirse Ronan, Margot Robbie, Jack Lowden, Martin Compston, David Tennant, Joe Alwyn, Brendan Coyle and Guy Pearce.  The film is scheduled to be released on November 2, 2018 by Focus Features.

Thomas Morgan (of Llantarnam): Thomas Morgan of Llantarnam (or Bassaleg, a branch of the Morgan of Tredegar) (1546–1606), of the Welsh Morgan of Monmouthshire, was a confidant and spy for Mary, Queen of Scots, and was involved in the Babington plot to kill Queen Elizabeth I of England.  In his youth, Thomas, a staunch Catholic, worked as Secretary of the Archbishop of York until 1568, and then for Lord Shrewsbury who had Mary under his care at this time.  Morgan's Catholic leanings soon brought him into the confidence of the Scottish queen and Mary enlisted Morgan as her secretary and go-between for the period extending between 1569 -1572 which coincinded with a series of important conspiracies against Elizabeth.  Morgan was imprisoned for 3 years in the Tower of London before exiling himself to France.

David Rizzio: David Rizzio, sometimes written as David Riccio or David Rizzo (c. 1533 – 9 March 1566), was an Italian courtier, born close to Turin, a descendant of an ancient and noble family still living in Piedmont, the Riccio Counts di San Paolo e Solbrito, who rose to become the private secretary of Mary, Queen of Scots.  Mary's husband, Lord Darnley, is said to have been jealous of their friendship, because of rumours that he had impregnated Mary, and joined in a conspiracy of Protestant nobles, led by Patrick Ruthven, 3rd Lord Ruthven, to murder him.  The murder was the catalyst for the downfall of Darnley, and it had serious consequences for Mary's subsequent career.  Mary was having dinner with Riccio and a few ladies-in-waiting when Darnley joined them, accused his wife of adultery and then had someone murder Riccio, who was hiding behind Mary.  Mary was held at gunpoint and Riccio was stabbed numerous times.  His body had over 50 wounds.

Saint Margaret of Scotland: Saint Margaret of Scotland (c. 1045 – 16 November 1093), also known as Margaret of Wessex, was an English princess of the House of Wessex.  Margaret was sometimes called "The Pearl of Scotland".  Born in exile in the Kingdom of Hungary, she was the sister of Edgar Ætheling, the shortly reigned and uncrowned Anglo-Saxon King of England.  Margaret and her family returned to the Kingdom of England in 1057, but fled to the Kingdom of Scotland following the Norman conquest of England in 1066.  In 1070 Margaret married King Malcolm III of Scotland, becoming Queen of Scots.  She was a very pious Roman Catholic, and among many charitable works she established a ferry across the Firth of Forth in Scotland for pilgrims travelling to St Andrews in Fife, which gave the towns of South Queensferry and North Queensferry their names.  Margaret was the mother of three kings of Scotland, or four, if Edmund of Scotland, who ruled with his uncle, Donald III, is counted, and of a queen consort of England.  According to the "Vita S. Margaritae (Scotorum) Reginae" ("Life of St. Margaret, Queen (of the Scots)"), attributed to Turgot of Durham, she died at Edinburgh Castle in Edinburgh, Scotland in 1093, merely days after receiving the news of her husband's death in battle.  In 1250 Pope Innocent IV canonized her, and her remains were reinterred in a shrine in Dunfermline Abbey in Fife, Scotland.  Her relics were dispersed after the Scottish Reformation and subsequently lost.  Mary, Queen of Scots at one time owned her head, which was subsequently preserved by Jesuits in the Scottish College, Douai, France, from where it was subsequently lost during the French Revolution.

Anna Throndsen: Anna Tronds (c. 1540–1607), known in English as Anna Throndsen and posthumously as Anna Rustung, was a Dano-Norwegian noblewoman.  In English and Scots history, Anna Throndsen is best known for her marriage to James Hepburn, 4th Earl of Bothwell (which later earned her the nickname "Skottefruen" (""The Scottish Lady""), a man who later married Mary, Queen of Scots.  Anna Throndsen is also known for her possible but much debated and disputed involvement in drafting some of the famous Casket Letters; these letters being the principal evidence used in the murder trial of Mary, Queen of Scots.

Mary, Queen of Scots: Mary, Queen of Scots (8 December 1542 – 8 February 1587), also known as Mary Stuart or Mary I, reigned over Scotland from 14 December 1542 to 24 July 1567.

Supporting paragraphs: David Rizzio Mary, Queen of Scots
Answer: Lord Darnley