THEORY: Largo will save us from Cogliacci
I think the creeps for this event are foreshadowing what is to come next.
We know that Cogliacci is putting souls into his automaton army. Who is there to fight them? Frogs, apparently! And who is a frog? Largo is a frog.
I think Largo is likely to be the main hero of the story in either Act 2 or 3 and that will explain the Radiant creeps.