Stuck on green path after arborun

I’m a noob, started playing today. Can’t get past that skeleton dragon that’s on the green path. I’ve read I have to access some underground maze but I don’t see any. Plz help

Train your arks, after 10-11 turns in the battle someone come to talk to you.

Did a person tell you not to stray off the green path? Because if so, you can’t beat him yet. You need to go to the town first, do some quests, and then fight him again.