Short answers, pulled from the story.
Henry Stuart, Lord Darnley (1546-1567) was king consort of Scotland as the second husband of Mary, Queen of Scots. Through his father Matthew Stewart, 4th Earl of Lennox, and his maternal grandmother Queen Margaret Tudor, daughter of King Henry VII, he held claims to both the Scottish and English thrones. His son by Mary, baptised Charles James, became King James VI of Scotland and James I of England.
Darnley was killed on the night of the 9th-the 10th of February 1567 at Kirk o' Field, Edinburgh. Two barrels of gunpowder exploded beneath the house where he slept, but his body was found in the orchard outside with no visible marks of violence. A post-mortem revealed internal injuries, and investigators concluded he had been smothered.
James Hepburn, 4th Earl of Bothwell, was the primary suspect and was tried in Edinburgh, but was found not guilty. Before his own execution in 1581, James Douglas, 4th Earl of Morton, admitted knowing of the murder plot and named Bothwell and Archibald Douglas as the 'chief actors.' Mary, Queen of Scots, was also suspected, and the Casket Letters were produced as evidence of her possible involvement.
On the 9th of March 1566, Darnley and Protestant Scottish nobles stabbed Mary's private secretary David Rizzio fifty-seven times. According to Thomas Randolph and the Earl of Bedford, the murder was Darnley's bid to force Mary to cede the Crown Matrimonial, the title that would have made him her successor if she died childless. The Earl of Morton and Lord Ruthven later told William Cecil that Darnley had initiated the plot because of his 'heich quarrel' and 'deadly hatred' of Rizzio.
Darnley was buried in the Royal Vault at Holyrood Abbey in 1567, but between 1776 and 1778 the vault was raided and his skull was stolen. In 1928, Karl Pearson published research on a candidate skull held at the Royal College of Surgeons. In 2016, Emma Price at the University of Dundee concluded the Royal College of Surgeons skull was a good match for Darnley, and a historical facial reconstruction was produced from it.
Darnley authored at least two poems printed in the Bannatyne Manuscript, compiled around 1570: 'Darnley's Ballet' and 'Gife langour makis men licht.' A third poem, 'Quhair luve is kendlit confortless,' is attributed to him with less certainty.