Larva pet
Larva make me so happy, and there's been a line stuck in my head for a bit from the larvalets, that they like to be held in a warm hand.
I propose that the larvalets allow for being held as an off hand item. They won't have an obvious counter, but they keep track of how many enemies you kill with them in your hand.
Maybe after a thousand, they'll spin into a little cocoon and be usable as an egg in the incubator! Larva pet! Possibly a pet for crit and vampire healing?