The bridge to the Mystic Isle is summoned at the weathered stone (9,5) in the Sidhe lands. You need the White Rose from the Fir'bolgs at (28,7) to achieve this (see Sidhe Lands).

The Mystic Isle once held a great settlement of Fir'bolgs, the city of Cantref y Gwaelod. Now it lies in ruins. The few Fir'bolgs remaining on the isle have sought shelter among an apple grove. The party can safely rest there.

The Fir'bolgs will fearfully explain that a great adventuring wizard known as Gwyddno brought back the sacred relic, the Cauldron of Cerredwhen, from one of his expeditions. His experiments with it led him to raise a monstrous swamp spirit, the Cenn Cruiach (Great Mound) from the fens. It now continues to raise its spawn through the power of the Cauldron. Some of the spawn are gathered at the heart of the swamp (63,21).

Enter the wizard Gwyddno's tower (45,15). Check the body in the entrance, it is the remains of Gwyddno and he retains his useful ring. Go downstairs to interrupt the Cenn Cruiach and his spawn. He possesses the Cauldron. The upper levels contain the various belongings of Gwyddno. They are protected by a guardian golem. Find the key and map to his secret cave at (45,11) wherein lies more magical treasure and another guardian golem. Return to the Fir'bolgs hiding in the apple grove, and leave the Isle and return to Rowan the Druid.

To north of the island lies a small burial ground (73,3) wherein is located a mighty spear, the Gae Bolga. Beware the guardians.