Steffon Darklyn
A knight of the queen's guard on Dragonstone, of Duskendale's old blood — loyal enough to try anything, including a riderless dragon.
A soul born at Duskendale, sworn to The Blacks — the Queen's Party, The Kingsguard, House Darklyn.
The fuller tale
Season Two
Ser Steffon Darklyn dies in fire on Dragonstone's slopes, trying to claim the riderless Seasmoke for the blacks.
Their story
A knight of Rhaenyra's own household guard on Dragonstone, and of Duskendale's old blood like his kinsman Gunthor, Steffon carries a loyalty to the black cause thorough enough that he volunteers for an assignment considerably more dangerous than his rank would normally require.
With Seasmoke left riderless since Laenor's departure from the story, and the war's desperate need for more dragons pushing the black council toward increasingly long-shot claiming attempts, Steffon puts himself forward to try his own Valyrian pedigree and a driftwood wand against a dragon that has already refused several other hopeful riders.
How it ends for them
On the screen. Burned trying to claim Seasmoke (S2·E6)
Lord commander of the queen's guard, he volunteered to claim the riderless Seasmoke with a driftwood wand and a Valyrian pedigree. The dragon wanted blood, not breeding: the fire took him on Dragonstone's slopes, and the claiming was left to bastards.
On the page. Burned in the Sowing (F&B, ch. 5)
He tried the riderless Seasmoke with a whip and a warrant and the blood of old Valyria, and burned for it on Dragonstone's slopes — proof, Gyldayn notes, that the dragons did their own choosing in the Sowing.
In the show, Steffon approaches the riderless Seasmoke on Dragonstone with the confidence of a man who believes ancestry alone should be sufficient qualification — the dragon disagrees violently, and the fire that follows kills him on the castle's slopes.
Fire & Blood records the same death during the Sowing, when the black council opens dragon-claiming to any hopeful with a plausible claim of Valyrian blood. Steffon burns for the attempt, one of several such deaths the book cites as proof that the dragons, whatever the desperate humans around them believed, were still doing their own choosing.
Their chapters, book by book
Where the page and the screen part
Both tellings agree on the manner and setting of his death, with the show's version staged as part of its broader dramatization of the desperate dragon-claiming period known in the histories as the Sowing.
Their journey
Where the two tellings send them to the same place the road runs whole; where they part, the screen keeps the left and the books the right.