Rikkit: a shiver of rock that became a stowaway
Rocky moon that is most likely a fragment of a massive celesial that crashed into Herco in the past, and de-orbited it closer to PE31H star.
Many of these fragments, including Rikkit, got imprisoned by Herco's gravity and travelled with the planet to the centre of the system.
Drifting at sprinter's pace around its' parent, Rikkit gathered enough of Herco's rings material to create a visible gap in them. Loose silicate regolith on Rikkit's surface most likely comes from there.
Rikkit as a rock of this size, shouldn't be that heavy - hence it is expected that it has iron core, most likely liquid, as the moon's insides are heated up by the tidal forces caused by Herco's closeness.