Coven Compass

The Coven Compass (カヴン＝コンパス) is a Mobile Fortress, operated by Witches.

Etymology
A usually refers to a group or gathering of witches.

Appearance
The Coven Compass is a giant disk of stone 200m in diameter and 10m thick. The top of the disk has sharp lines running in each direction from the center, resembling an actual compass. Dozens of ropes hang down loosely from the underside.

Principles
The fortress hovers about 20m above the ocean and has several countermeasures to prevent anti-flying spells from bringing it down.

On top of the fortress is a device designed to fire a large-scale flash spell which can be used to "fry" invaders. The fortress also possesses the capacity for long-range bombardment, with an estimated 'effective' range of approximately 330km.

British Royal Family Arc
When the coup d'état was initiated at midnight on October 18th, the Coven Compass, near Islay, was one of the many sites that were attacked by the knights and a battle ensued between them and the witches stationed on the fortress. Following Smartvery's suggestion concerning how the Curtana Original only provides the knights with power within the UK's borders, they travel just outside the border, creating a standstill between them.

After Carissa returned to Buckingham Palace in order to tune the unstable Curtana, the Anglicans made use of a flash spell relayed from the fortress in conjunction with the safety devices under the palace in order to send the Curtana Original's power out of control at 2:30 AM.

The fortress was later used by the witches to launch long-range attacks on Buckingham Palace during the final battle of the coup d'état, beginning at 3 AM. At this point, it had begun to list due to battle damage. The tremendous power of the blasts was augmented by shots from Princess Villian's bowgun into a destructive stream of water and a barrage of golf ball-sized spheres.

Trivia

 * The actual full range of the "flash attack" from the Coven Compass was never directly stated, however Smartvery mentioned that 500 kms was a little bit more than 1.5 higher than the actual range of the weapon, meaning that 330 km is only a reasonable estimate born from that comment.