Lost Underworld
Honey, I Shrunk The Heroes
The Chomposaur and other enemies are pretty beefy so stay on guard.
Another thing to note is that as you walk around, periodically the ground will shake causing your heroes to be frozen for a moment. That would be the geysers around the map. Each of them act as spas that will restore your party in various ways.
Red treats status ailments, Blue treats HP/PP.
Towards the center of the map there is a gated village.
When you walk up to the gate one of then Tenda's will smell the Tendakraut that you're carrying with you.
In exchange for the Tendakraut you will gain access to the village.
One of the Tenda will tell you about the Fire Spring located southwest of the village.