I found a new subdungeon (or at least one I hadn't seen before).
You get a little area of plants and a vamp.

Kill the vamp and you get a small item that looks like a scroll, you can read it.

All the plants you can one shot and none of them have any negative effects. When you kill one it appears in the area up the top of the screen. I think you are meant to hit the plants in the right order to complete the recipes. I did two but have no idea if they worked. I didn't get any items, I may have got a buff though because I wasn't paying attention to stats.
edit: I stumbled across it again and was more careful this time.
Health Broth = +5 Max Health
Magi Soup = +1 Max Mana
Strength Syrup = +1 Base Attack
Caramel Conversions = +20 Conversion Points
Cake of Attack Bonus = +5% Attack Bonus