Driffer: the undisputed heavyweight champion
Driffer, the innermost moon of ice giant Santri, is by all means the biggest and the heaviest moon in the whole PE31H system. Being almost three times heavier and 50% bigger than Striker, the smallest globe in the system, Driffer could be easily classified as a planet, if it orbited around the star.
Heated up by tidal forces of the parent planet and two other most massive moons in the system, Driffer has most likely a liquid iron core. Still, the distance from the star and lack of atmosphere makes it a frigid place. Cracks and chaps are clearly visible all across the moon's surface - this suggests that at some point in the past water could have been present there - apparently it has evaporated or at least greatly reduced in volume by now.
Do you have the guts to visit the outskirts of the PE31H system and see the heavyweight champion of all the moons with your own eyes? Consider the view of the vast Santri, the most colossal planet around, as a bonus then...