The fifteenth arcanum gives brightness and power over attention. Such a person is noticeable and interesting, and knows how to gather people around them — a born organiser.
The same ability works in another way too: they understand well what a person will give in to, and they can make use of it. Setting people against each other, giving a nudge, arranging matters so that things come out their way — all of this comes easily to them, and not always consciously.
So the whole question here is one of direction. Turned one way, this is a leader around whom things get done; turned the other, this is the one after whom people stop trusting each other.
The weak point is boredom. The fifteenth arcanum begins to play with people precisely when it has nothing to occupy itself with.