"Phobos and Deimos Castle" orbited the planet Mars and in the manga, it was the palace of Princess Mars, given to her by Queen Serenity when she was born.
In Act 41, each of the Solar System Sailor Senshi called upon the power of their castles and directed it to the Holy Grail, which allowed Sailor Moon to transform into Eternal Sailor Moon.
Trivia[]
- Phobos and Deimos are the two moons that orbit the planet Mars in real life.