The explorer frog has the only real way to track the Mothmen in the darkness, which is an echolocation croak, which brings back a sonar ping signal.
We had originally intended for more than just combat goals, and the first level was intended to be the post tutorial level, where you were going to run to an escape area... sadly we ran out of time, and where the death victory conditions still worked for the final map (checking on the king's health vs the moth's health) that didn't really work for the fist map where you could get in a slow-painful-loss condition once the Unicorn Frog was downed.
Having played so many turn based strategy games (X-Com, Battle Brothers, Menace, Xenonauts, Phoenix Point) I'm still ashamed I've never checked out any of the Fire Emblem series.