At least two years after her second downfall, Morgana Pendragon used it as a hideout for herself, Aithusa, her men and Ruadan and 'practically ripped it apart' in her search for the Diamair. The throne room was virtually empty, except for Morgana's throne, some torches and a few statues. The castle also included passages, a bedroom and a dining room, of which were covered in cobwebs. Torches were used to light rooms in the fortress. The fortress was also occupied by the dragon Aithusa who could fit in Morgana's bedroom and had access to the caves.
The physical appearance of the fortress itself is a tall, ragged tower with a few turrets and a few windows. There is a strong outer-wall. Underneath are hidden caves, dug by Morgana's slaves, that can only be accessed by a tunnel leading from the inner-courtyard. These mines are also home to the Euchdag, the key to all knowledge, that Morgana and Ruadan are searching for. The main gate is guarded by two Saxons.
Sir Gwaine leads a patrol of Knights including Percival to investigate a 'shadow' over the lands of Albion. As soon at the fortress is in sight, they get attacked by Magic Wolves and then captured by Morgana. Morgana and Ruadan then use them to assist the Saxons in mining for the mysterious key to 'Arthur's Bane'. While mining, Gwaine sees a light, he then follows if before he is caught off-task and gets beaten by Saxon guards on the spot. The mysterious light he was curious about, turns out to be the Euchdag, which could be what Morgana was looking for (Arthur's Bane).
- "Īsmere" is Anglo-Saxon for "ice-lake".