You receive this quest from Robert who is in the Boardroom of Gods.
He says to find Queen Guen and Taran the Thunder God, you'll have to search Castle Loegria in the East and the Fortress of Glass in the West.
You will receive the Find the Key Quest.
Talk to Dylan the Guard at the entrance of the Castle of Loegriain the Village of Albion.
You will receive the Guard's Key.
Open the entrance to the castle with the Guard's Key.
You will lose the Guards Key.
Use the disarm spell on the barricade to the left.
Enter the Castle.
Find a kid named who will ask you to answer a riddle.
The answer to the riddle is Bumblebee.
Find the ghost of King Locrinus in the Castle. He's on the 2nd floor.
He says to go to the Fortress of Glass and kill Guen and Taran the Thunder to avenge his death and free his daughter, Habren.
You will receive the Glass Key.
Return to Robert in the Boardroom of gods and talk to him.
The Find the Key quest will be solved
You'll receive Robert's Lancer and 7500 Experience.