I found Coryool to be singularly useless for that part of the game. Sparks and his fire magic will decimate a large portion of the enemies you'll encounter there, though.
If I remember correctly, you can only leave rillia at this point if you talk to kevin the explorer, and only to the places he is willing to take you. No going back to other places yet, I think.
My dwellings: The Glade and Eridani's Anyway, if I wanted a complex story led by dynamic characters that aren't easily categorised into facile dichotomies of good and bad with no clear arc or easily predicted outcome, I'd have left the theatre and lived my damn life. Brownian
Hello! I took on the root skeleton when I was finished with everything in the witch woods! The first time I took him on I died over and over again, but it was easy after leveling up! Also, if I remember correctly, totems of evil were helpful.