I've noticed that while not as in involved in day-to-day gameplay elements of the Grand Companies, the Grand Marshals have been appearing in story events. Like Grand Storm Marshal Eynzahr Slafyrsyn, who was involved in the Leviathan incident and used to be Mistbeard. Then there's Grand Flame Marshal Eline Roaille, who was a mole placed by Emperor Varis. And we know how Grand Crystal Marshal Ilberd turned out.....
But what about the Grand Serpent Marshal of the Twin Adders? I don't think I've seen him or her at all.