This grand Gothic cathedral was constructed beneath the ground to provide a nucleus for the Templeisen religion and venerate the Grail. Richly decorated and provided with massive brass organs, the cathedral served its purpose for a time, allowing Tobias to deliver sermons based on his vision to the knights. Unfortunately, it fell into disuse as time passed by and by 2012, it is home to a very hungry leo.
The Cathedral is shaped like a donut, a square one, with the cathedral vestry and organs in the center. There is an opening in the floor to the right-hand side, leading to the crypt below. Beyond it is a door leading to the Cathedral pulpit. Opposite the pulpit is a locked door leading to the fight room and exit from Aeternis, which will open only if you have the Holy Grail. The large door with twelve coats of arms of the knights hides the access to the Grail.
The most important issue here is the hungry, hungry leo. To get rid of him, either enter the Cathedral through the Cathedral pulpit, making sure to enter the crypt and approach the knight relief behind the bars (the leo will become curious and fall in, killing itself and releasing Claude Lancet from his casket; you're safe from his wrath). Otherwise, enter the Cathedral vestry, dashing madly away from the beast, then drop the organs using the chain next to the organ keyboard. The beast is trapped behind them afterwards.
The massive door leading to the Grail is opened using the brass lever recovered from the organs inside the vestry to connect the gears.
- Brass lever: This plot-critical item needs to be removed by vandalizing the brass organs. It can be found among them afterwards.