This is Steve Toussaint as Lord Corlys Velaryon, also known as The Sea Snake.
His nickname of The Sea Snake is due to his time as the most famous nautical adventurer in the history of Westeros.
At any rate, I wasn’t too far off, because Lord Corlys here is of House Velaryon, a Valyrian bloodline which is just as old as that of House Targaryen.
I will admit, this image made me very excited at first, because I thought we were getting a black Targaryen.