I see that it's recognized as Malfi V-c, but that just means what's Malfi V?

I recall that the planet Malfi was a Hive world, but I don't think Malfi's exact position in the system (perhaps it is Malfi V?) or the type any other planetary bodies were ever established. Calixis had far too many systems for them to bother fleshing out such details, I guess.

Main Malfi as Malfi II (Ascension, p.216), also Malfi VIII "Borusa" is mentioned, but can't remember anything official about Malfi V.

If Malfi V is 3 steps farther from the star than a habitable world, and its moon is an agri-world (especially if "c" means it's 3rd moon), it's probably a gas giant.