There are a number of items of interest in Enhasa. The blue symbol on the floor in the northwest corner will restore your HP and MP like resting. You'll also encounter Doreen, a creature resembling Masa and Mune, and the blue-haired child Janus here.
You'll learn the secret of the elemental books in Kajar. To open a secret passage, use the book of water (northeast), then wind (northwest), and finally fire (at the entrance). Inside you'll find a Nu. Speak to him to start a tough battle with six Nus.
The Nus can be difficult, but the secret is in understanding how they attack. Three will always reduce your HP to 1 (the lower middle, upper right, and upper left), while the other three will always deal 1 damage. Either set is mostly harmless without the other, though I'd recommend getting rid of the ones that deal 1 damage so you can stop worrying immediately.