Mariner Castle

Mariner Castle (マリナー・キャッスル) orbited the planet Mercury, and in the manga and Sailor Moon Crystal, it was the palace of Princess Mercury, given to her by Queen Serenity when she was born.

In Act 48 of the manga and in Sailor Moon Eternal, the Solar System Sailor Princesses called upon the power of their castles and directed it to the Holy Grail, which gave Super Sailor Moon the power to transform into Eternal Sailor Moon.

Trivia

• Mariner Castle's name is derived from the name of a space probe sent to explore Mercury in the 1970s.