Ultima VI: The False Prophet/Swamp cave

The swamp cave in Ultima 6 is located exactly where the mage Grendel lived in Ultima 5. Now, the dead body of a mage can be found on the deepest level of the swamp cave: it seems logic that this may be the body of Grendel himself, although there are no stronger clues.

Getting ready
Before exploring the swamp cave, make sure the Companions are equipped with the following:
 * Swamp boots for every party member; they can be purchased in Yew.
 * The Telekinesis spell and/or both the Vanish & Reappear spells; they can all be purchased from Xiao near the Lycaeum.

Getting there
The swamp cave is located at 0°N, °E. It is east from Britain, near the coast. Still, it can also be reached from the land; the advantage is: you can meet a few weak enemies and earn some experience and gold.

Leave Britain walking to the east. Follow the road towards Minoc. As soon as you get past Kafiristan Pass, leave the Mudfish Road and continue east and south along the mountains. Follow the coast to the west until you can proceed no further. Retrace your steps a little bit to the north-east, and you can find the entrance to the Swamp Cave.

Dungeon map
Click to enlarge.

Floor 1
Hug the wall to your left and explore teh souther part of the cave: you will find a gem and 101 gold coins. Continue to the west, and you will see a ladder down: ignore it, there is another one that bring to the same area. Continue hugging the left wall until you see a subterranean river and a skiff on the other side: cast either Telekinesis twice, or Vanish and Reappear, so that you can cross the river and get 10 gold nuggets. Continue north until you get to the ladders down.

Floor 2
As before, hug the left wall and proceed north-east. At the dead end you will find lots of lost equipment, including a rare gargoyle helm. Now explore south. after you pass a bridge, start hugging the right wall: you will see several underground rivers and face many enemies, until you will reach a barrier of force fields. Do not dispel the force fields: you can walk under them later. Continue hugging the right wall until you see the ladder down.

Floor 3
Hug the left wall, pass the two bridges over the underground rivers, then take the ladder up. You are now on the other side of the force fields. Fight the enemies to earn experience and equipment to be sold. Leave the sheep alone: if you attack them, you will lose Karma points.

Back on the third floor, continue straight south until you get to the ladder down.

Floor 4
Here is where the body of the mage, supposedly Grendel from Ultima 5, can be found. It is in an alcove straight to the south. Search the body and get one of each of the rarest items in the game, including a storm cloak.

OPEN QUESTION: The plain, yellow ring on the mage appears out of place. Maybe you can cast the Lv.6 spell "Enchant" on it and turn it into a different ring?

The skiff on the lake shore is not necessary. You can carry it to the very north-west end of the cave floor and use it to cross a river. Still, there is nothing on the other side of the river.

Explore at leisure the deeper floor of the swamp cave: there are many enemies that can raise your experience.

Summary
Back on the surface, sell all the weapons and armors you need not; the wooden shields cannot be sold at all. You can cast the "Enchant" spell on the staff and turn it into a spellcasting staff. In Britain, you can turn all the gold nuggets in gold coins.