Istarius: that's where impossible turns up to be true
Istarius is special, very special... It is the only gaseous moon discovered so far. This second natural satellite of Santri is the third heaviest, but also the third smallest moon in the system. How a celestial that small can be that heavy? Opinions vary but one is sure - Istarius must have a supermassive core - likely made of iron, or something even heavier. Potentially, that is why the moon accreted that much of helium and hydrogen to become what it is today.
Due to the distance from the PE31H star, Istarius is a freezing cold place. Yet, tidal forces generated by Istarius' vast neighbours and rapid rotation around the parent planet must heat up the moon's interior, causing strong convection-driven winds that circle Istarius at incredible speeds, forming distinctive elongated, moon-wide patterns out of whiteish clouds.
Gear up and carry out a lenghty burn to the very border of PE31H system to witness its' bizarre uniqueness. There is yet a hefty lot of mysteries to be uncovered there.