Outside of the dome.

Outside of the dome was a large bridge of dimensional energy with liquid energy covering over it so that people could walk onto it without dying or anything. Also, a small radius of the sea around Tigen's dome was stiffened Liquid Energy that would also enable people to walk on it. Battles could ensue on either the bridge or the stiffened liquid... hell, it would actually be quite fun. There are also a great many vines surrounding the door into the liquid and if Tigen wants, there could be some pumpkin guards... Make sure to know before popping in, or they could devour you.