George R.R. Martin has called Beric a "fire wight" and a foreshadowing for Jon Snow's inevitable resurrection, and most people think Melisandre will give Jon R'hllor's "last kiss" at some point, so it's an important thing to understand... but it also turns out to help reveal the secret origins of R'hllorism - an origin that has roots in both Asshai and Westeros, and the events of the Long Night.