Selkie Aquarium

Selkie Aquarium (セルキー＝アクアリウム) refers to a series of submarine-type mobile fortresses owned by the United Kingdom. There are least 8 of these mobile fortresses.

Principles
Selkie Aquarium is a submarine-type mother ship for Magicians carrying out underwater activities. They are usually used to anticipate and quickly respond to any definite movements made in the border between England and France, the English Channel.

Like the Coven Compass, the Selkie Aquariums are capable of firing a large-scale flash bombardment.

British Halloween
Some time during the events of Carissa's coup d'état, as the Selkie Aquariums were used by magicians of the Anglican Church, the knights and the Royal Navy engage at least two of the Selkie Aquariums in battle, Selkie 3 and 8. It is unknown what happened to Selkie 6 and 7, though they are likely destroyed.

The remaining Selkie Aquariums that are not caught in a battle with the Knights of England, along with the Coven Compass, later aid the Anglican Church in the Battle of Buckingham Palace during the opening bombardment on the palace, managing to strike it 100–200 times.