Jewel of Light
Summons a fairy princess to provide light 'A glowing gemstone that houses a powerful fairy.'
The light of the fair folk illuminates all
5Dropped by
a light pet and nothing more
It lights the area around the fairy and around you, and that is the entire feature list. There is no treasure sensing like the tentacle and no way to park it somewhere useful the way the Wisp in a Bottle lets you. Brightness matches the other top-end light pets exactly, so the only thing you are choosing is the pink tint and a fairy that sits just above and behind your shoulder instead of wandering.
worth farming for?
It only exists as a Master Mode drop from the Empress, and anyone beating her repeatedly on that difficulty already owns a light pet that does the same job. Take it if it falls out, but there is no reason to keep rerunning that fight for it. The Suspicious Looking Tentacle is still the one to carry when you are exploring.
the reused fairy
The pet is nearly the same creature the Frozen Crown summons, down to how it flies.