ToME WikiThe Submerged Ruins is an inherently dangerous environment. You will need water-breathing to survive in it for very long, though short adventures made with plenty of healing potions are possible.
Boss: Ar-Pharazon the Golden. Au Pharazon is not a very tough boss, unless he gets a lucky summon. He carries Toris Mejistos, the best amulet in the game for spellcasters.
This dungeon is far to the west of Bree, and northwest of the Sandhole, surrounded by deep water tiles. "There is a submerged way to the lost land of Numenor." You are in threat of a deep water ambush.
You will never be ambushed if you are level 50 (is this the minimum?). In this situation it is a good idea to carry rations of food instead of scrolls of satisfy hunger, because you can eat the rations without dropping to a lower map level where you can meet monsters. If being ambushed is possible for you, walk in the more detailed map level and hug the handy map borders. You will never be ambushed if you are not on the wilderness map.