He rules a United Lordran that incorporates both Anor Londo and Izalith, via a Political Marriage set up, ironically, by Gwyn himself. As Nameless is the Heir to the Lightning, Gwyn thought it’d be most appropriate to tie his son to one of daughters of the Witch of Izalith. Quelana was chosen, as Gwyn thought that the combination of The Heir to the Lightning and The Mother of Pyromancy would be too good to let slip.
His plan worked... and blew up spectacularly in his face.
As a result of NK’s victory (here is refered to as Gwyntaran), dragons, gods and humans live in (relative) harmony. Of course, there are still those who stick to the old ways, and many who will never forgive him for allying himself with the dragons and ousting his own father, meaning a large portion of the original army of Silver Knights and other warriors departed rather than serve the ‘usurper’.
On the other hand, he still has the Storm King and Ornstein, who this time sided with NK as Gwyn’s flaws became more pronounced. And so, as NK’s first Knight and oldest friend, he sided with the son against the father. The Leo Knight now has the job being head of the royal guard and the overall commander of the armed forces.
Since he incorporates humans to his kingdom, he also finds a new source of recruits for the army... including a band of knights dedicated to jolly cooperation...
The second half will focus on Gwyndolin