Willowisp
What it does: It snatches up Children and teleports them to another room. Possibly while giggling.
How to make it:
Grind up a Hawk in a Forest Shrine and watch this come out.
What it makes:
If you toss a Willowisp into an Ancient Mortar, it’ll make a Boar. Somehow.
And if you get three Willowisps in with an Ancient Mortar, you’ll get a Potion of Fear.