There are level 20 (or so) black ring members along the beach beside the primordial cave, and the one behind where the anti-dragon shields are/were. The other beach has level 21 imps, and goes past the depleted ore mine, most of which should be fine to do now (there is a level 27 beholder near the end of the mine I managed to take out at level 22, using a bow and my creature as a shield until he was killed, then rush attacking to finish him off before he could hit me once or twice and kill me).
The primordial cave can be left until later. Once the barrier is down (3 levers in the bunker) it is the path past the depleted ore mine which leads to High Halls and the harbour. Swim or fly to the northern beach in the channel leading north east.
There is also a cave in the mountains just to the left of where the anti-dragon shields ended around the bunker, with about level 21-22 opponents IIRC.
