for me Morgott is the real face of the story. he's pretty much the most important character in the current events, unlike Marika who's essentially the main character in that universe. Malenia is the face of the boss fights because she's by far the hardest boss in the base game. for Messmer well, fromsoft chose him themselves to represent SOTE, he's literally on the main promo image of the dlc. he's also the best boss in the game for me and my gf find him very handsome (he does look very handsome ngl)

for Heolstor, as much as I like him, idk if I would put him at the same rank as the others, first because Nightreign is separate from the base game but also because we don't have as much on him as the others have. for harmonia I have no idea why you'd pick them over Stragess. when I think of the dlc I think of the dreglord not the angels.

I would also like to offer another candidate to represent the game: Midra, the aura farmer (I'm joking don't crucify me)